Issue #7989: Added pure python implementation of the datetime module.

1 files changed, 2087 insertions, 0 deletions

diff --git a/Lib/datetime.py b/Lib/datetime.py
new file mode 100644
index 0000000..7b7b8aa
--- /dev/null
+++ b/Lib/datetime.py
@@ -0,0 +1,2087 @@
+"""Concrete date/time and related types -- prototype implemented in Python.
+
+See http://www.zope.org/Members/fdrake/DateTimeWiki/FrontPage
+
+See also http://dir.yahoo.com/Reference/calendars/
+
+For a primer on DST, including many current DST rules, see
+http://webexhibits.org/daylightsaving/
+
+For more about DST than you ever wanted to know, see
+ftp://elsie.nci.nih.gov/pub/
+
+Sources for time zone and DST data: http://www.twinsun.com/tz/tz-link.htm
+
+This was originally copied from the sandbox of the CPython CVS repository.
+Thanks to Tim Peters for suggesting using it.
+"""
+
+import time as _time
+import math as _math
+
+def _cmp(x, y):
+    return 0 if x == y else 1 if x > y else -1
+
+MINYEAR = 1
+MAXYEAR = 9999
+_MAXORDINAL = 3652059 # date.max.toordinal()
+
+# Utility functions, adapted from Python's Demo/classes/Dates.py, which
+# also assumes the current Gregorian calendar indefinitely extended in
+# both directions.  Difference:  Dates.py calls January 1 of year 0 day
+# number 1.  The code here calls January 1 of year 1 day number 1.  This is
+# to match the definition of the "proleptic Gregorian" calendar in Dershowitz
+# and Reingold's "Calendrical Calculations", where it's the base calendar
+# for all computations.  See the book for algorithms for converting between
+# proleptic Gregorian ordinals and many other calendar systems.
+
+_DAYS_IN_MONTH = [None, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+
+_DAYS_BEFORE_MONTH = [None]
+dbm = 0
+for dim in _DAYS_IN_MONTH[1:]:
+    _DAYS_BEFORE_MONTH.append(dbm)
+    dbm += dim
+del dbm, dim
+
+def _is_leap(year):
+    "year -> 1 if leap year, else 0."
+    return year % 4 == 0 and (year % 100 != 0 or year % 400 == 0)
+
+def _days_before_year(year):
+    "year -> number of days before January 1st of year."
+    y = year - 1
+    return y*365 + y//4 - y//100 + y//400
+
+def _days_in_month(year, month):
+    "year, month -> number of days in that month in that year."
+    assert 1 <= month <= 12, month
+    if month == 2 and _is_leap(year):
+        return 29
+    return _DAYS_IN_MONTH[month]
+
+def _days_before_month(year, month):
+    "year, month -> number of days in year preceeding first day of month."
+    assert 1 <= month <= 12, 'month must be in 1..12'
+    return _DAYS_BEFORE_MONTH[month] + (month > 2 and _is_leap(year))
+
+def _ymd2ord(year, month, day):
+    "year, month, day -> ordinal, considering 01-Jan-0001 as day 1."
+    assert 1 <= month <= 12, 'month must be in 1..12'
+    dim = _days_in_month(year, month)
+    assert 1 <= day <= dim, ('day must be in 1..%d' % dim)
+    return (_days_before_year(year) +
+            _days_before_month(year, month) +
+            day)
+
+_DI400Y = _days_before_year(401)    # number of days in 400 years
+_DI100Y = _days_before_year(101)    #    "    "   "   " 100   "
+_DI4Y   = _days_before_year(5)      #    "    "   "   "   4   "
+
+# A 4-year cycle has an extra leap day over what we'd get from pasting
+# together 4 single years.
+assert _DI4Y == 4 * 365 + 1
+
+# Similarly, a 400-year cycle has an extra leap day over what we'd get from
+# pasting together 4 100-year cycles.
+assert _DI400Y == 4 * _DI100Y + 1
+
+# OTOH, a 100-year cycle has one fewer leap day than we'd get from
+# pasting together 25 4-year cycles.
+assert _DI100Y == 25 * _DI4Y - 1
+
+def _ord2ymd(n):
+    "ordinal -> (year, month, day), considering 01-Jan-0001 as day 1."
+
+    # n is a 1-based index, starting at 1-Jan-1.  The pattern of leap years
+    # repeats exactly every 400 years.  The basic strategy is to find the
+    # closest 400-year boundary at or before n, then work with the offset
+    # from that boundary to n.  Life is much clearer if we subtract 1 from
+    # n first -- then the values of n at 400-year boundaries are exactly
+    # those divisible by _DI400Y:
+    #
+    #     D  M   Y            n              n-1
+    #     -- --- ----        ----------     ----------------
+    #     31 Dec -400        -_DI400Y       -_DI400Y -1
+    #      1 Jan -399         -_DI400Y +1   -_DI400Y      400-year boundary
+    #     ...
+    #     30 Dec  000        -1             -2
+    #     31 Dec  000         0             -1
+    #      1 Jan  001         1              0            400-year boundary
+    #      2 Jan  001         2              1
+    #      3 Jan  001         3              2
+    #     ...
+    #     31 Dec  400         _DI400Y        _DI400Y -1
+    #      1 Jan  401         _DI400Y +1     _DI400Y      400-year boundary
+    n -= 1
+    n400, n = divmod(n, _DI400Y)
+    year = n400 * 400 + 1   # ..., -399, 1, 401, ...
+
+    # Now n is the (non-negative) offset, in days, from January 1 of year, to
+    # the desired date.  Now compute how many 100-year cycles precede n.
+    # Note that it's possible for n100 to equal 4!  In that case 4 full
+    # 100-year cycles precede the desired day, which implies the desired
+    # day is December 31 at the end of a 400-year cycle.
+    n100, n = divmod(n, _DI100Y)
+
+    # Now compute how many 4-year cycles precede it.
+    n4, n = divmod(n, _DI4Y)
+
+    # And now how many single years.  Again n1 can be 4, and again meaning
+    # that the desired day is December 31 at the end of the 4-year cycle.
+    n1, n = divmod(n, 365)
+
+    year += n100 * 100 + n4 * 4 + n1
+    if n1 == 4 or n100 == 4:
+        assert n == 0
+        return year-1, 12, 31
+
+    # Now the year is correct, and n is the offset from January 1.  We find
+    # the month via an estimate that's either exact or one too large.
+    leapyear = n1 == 3 and (n4 != 24 or n100 == 3)
+    assert leapyear == _is_leap(year)
+    month = (n + 50) >> 5
+    preceding = _DAYS_BEFORE_MONTH[month] + (month > 2 and leapyear)
+    if preceding > n:  # estimate is too large
+        month -= 1
+        preceding -= _DAYS_IN_MONTH[month] + (month == 2 and leapyear)
+    n -= preceding
+    assert 0 <= n < _days_in_month(year, month)
+
+    # Now the year and month are correct, and n is the offset from the
+    # start of that month:  we're done!
+    return year, month, n+1
+
+# Month and day names.  For localized versions, see the calendar module.
+_MONTHNAMES = [None, "Jan", "Feb", "Mar", "Apr", "May", "Jun",
+                     "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"]
+_DAYNAMES = [None, "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
+
+
+def _build_struct_time(y, m, d, hh, mm, ss, dstflag):
+    wday = (_ymd2ord(y, m, d) + 6) % 7
+    dnum = _days_before_month(y, m) + d
+    return _time.struct_time((y, m, d, hh, mm, ss, wday, dnum, dstflag))
+
+def _format_time(hh, mm, ss, us):
+    # Skip trailing microseconds when us==0.
+    result = "%02d:%02d:%02d" % (hh, mm, ss)
+    if us:
+        result += ".%06d" % us
+    return result
+
+# Correctly substitute for %z and %Z escapes in strftime formats.
+def _wrap_strftime(object, format, timetuple):
+    year = timetuple[0]
+    if year < 1900:
+        raise ValueError("year=%d is before 1900; the datetime strftime() "
+                         "methods require year >= 1900" % year)
+    # Don't call utcoffset() or tzname() unless actually needed.
+    freplace = None # the string to use for %f
+    zreplace = None # the string to use for %z
+    Zreplace = None # the string to use for %Z
+
+    # Scan format for %z and %Z escapes, replacing as needed.
+    newformat = []
+    push = newformat.append
+    i, n = 0, len(format)
+    while i < n:
+        ch = format[i]
+        i += 1
+        if ch == '%':
+            if i < n:
+                ch = format[i]
+                i += 1
+                if ch == 'f':
+                    if freplace is None:
+                        freplace = '%06d' % getattr(object,
+                                                    'microsecond', 0)
+                    newformat.append(freplace)
+                elif ch == 'z':
+                    if zreplace is None:
+                        zreplace = ""
+                        if hasattr(object, "utcoffset"):
+                            offset = object.utcoffset()
+                            if offset is not None:
+                                sign = '+'
+                                if offset.days < 0:
+                                    offset = -offset
+                                    sign = '-'
+                                h, m = divmod(offset, timedelta(hours=1))
+                                assert not m % timedelta(minutes=1), "whole minute"
+                                m //= timedelta(minutes=1)
+                                zreplace = '%c%02d%02d' % (sign, h, m)
+                    assert '%' not in zreplace
+                    newformat.append(zreplace)
+                elif ch == 'Z':
+                    if Zreplace is None:
+                        Zreplace = ""
+                        if hasattr(object, "tzname"):
+                            s = object.tzname()
+                            if s is not None:
+                                # strftime is going to have at this: escape %
+                                Zreplace = s.replace('%', '%%')
+                    newformat.append(Zreplace)
+                else:
+                    push('%')
+                    push(ch)
+            else:
+                push('%')
+        else:
+            push(ch)
+    newformat = "".join(newformat)
+    return _time.strftime(newformat, timetuple)
+
+def _call_tzinfo_method(tzinfo, methname, tzinfoarg):
+    if tzinfo is None:
+        return None
+    return getattr(tzinfo, methname)(tzinfoarg)
+
+# Just raise TypeError if the arg isn't None or a string.
+def _check_tzname(name):
+    if name is not None and not isinstance(name, str):
+        raise TypeError("tzinfo.tzname() must return None or string, "
+                        "not '%s'" % type(name))
+
+# name is the offset-producing method, "utcoffset" or "dst".
+# offset is what it returned.
+# If offset isn't None or timedelta, raises TypeError.
+# If offset is None, returns None.
+# Else offset is checked for being in range, and a whole # of minutes.
+# If it is, its integer value is returned.  Else ValueError is raised.
+def _check_utc_offset(name, offset):
+    assert name in ("utcoffset", "dst")
+    if offset is None:
+        return
+    if not isinstance(offset, timedelta):
+        raise TypeError("tzinfo.%s() must return None "
+                        "or timedelta, not '%s'" % (name, type(offset)))
+    if offset % timedelta(minutes=1) or offset.microseconds:
+        raise ValueError("tzinfo.%s() must return a whole number "
+                         "of minutes, got %s" % (name, offset))
+    if not -timedelta(1) < offset < timedelta(1):
+        raise ValueError("%s()=%s, must be must be strictly between"
+                         " -timedelta(hours=24) and timedelta(hours=24)"
+                         % (name, offset))
+
+def _check_date_fields(year, month, day):
+    if not isinstance(year, int):
+        raise TypeError('int expected')
+    if not MINYEAR <= year <= MAXYEAR:
+        raise ValueError('year must be in %d..%d' % (MINYEAR, MAXYEAR), year)
+    if not 1 <= month <= 12:
+        raise ValueError('month must be in 1..12', month)
+    dim = _days_in_month(year, month)
+    if not 1 <= day <= dim:
+        raise ValueError('day must be in 1..%d' % dim, day)
+
+def _check_time_fields(hour, minute, second, microsecond):
+    if not isinstance(hour, int):
+        raise TypeError('int expected')
+    if not 0 <= hour <= 23:
+        raise ValueError('hour must be in 0..23', hour)
+    if not 0 <= minute <= 59:
+        raise ValueError('minute must be in 0..59', minute)
+    if not 0 <= second <= 59:
+        raise ValueError('second must be in 0..59', second)
+    if not 0 <= microsecond <= 999999:
+        raise ValueError('microsecond must be in 0..999999', microsecond)
+
+def _check_tzinfo_arg(tz):
+    if tz is not None and not isinstance(tz, tzinfo):
+        raise TypeError("tzinfo argument must be None or of a tzinfo subclass")
+
+def _cmperror(x, y):
+    raise TypeError("can't compare '%s' to '%s'" % (
+                    type(x).__name__, type(y).__name__))
+
+class timedelta:
+    """Represent the difference between two datetime objects.
+
+    Supported operators:
+
+    - add, subtract timedelta
+    - unary plus, minus, abs
+    - compare to timedelta
+    - multiply, divide by int/long
+
+    In addition, datetime supports subtraction of two datetime objects
+    returning a timedelta, and addition or subtraction of a datetime
+    and a timedelta giving a datetime.
+
+    Representation: (days, seconds, microseconds).  Why?  Because I
+    felt like it.
+    """
+    __slots__ = '_days', '_seconds', '_microseconds'
+
+    def __new__(cls, days=0, seconds=0, microseconds=0,
+                milliseconds=0, minutes=0, hours=0, weeks=0):
+        # Doing this efficiently and accurately in C is going to be difficult
+        # and error-prone, due to ubiquitous overflow possibilities, and that
+        # C double doesn't have enough bits of precision to represent
+        # microseconds over 10K years faithfully.  The code here tries to make
+        # explicit where go-fast assumptions can be relied on, in order to
+        # guide the C implementation; it's way more convoluted than speed-
+        # ignoring auto-overflow-to-long idiomatic Python could be.
+
+        # XXX Check that all inputs are ints or floats.
+
+        # Final values, all integer.
+        # s and us fit in 32-bit signed ints; d isn't bounded.
+        d = s = us = 0
+
+        # Normalize everything to days, seconds, microseconds.
+        days += weeks*7
+        seconds += minutes*60 + hours*3600
+        microseconds += milliseconds*1000
+
+        # Get rid of all fractions, and normalize s and us.
+        # Take a deep breath <wink>.
+        if isinstance(days, float):
+            dayfrac, days = _math.modf(days)
+            daysecondsfrac, daysecondswhole = _math.modf(dayfrac * (24.*3600.))
+            assert daysecondswhole == int(daysecondswhole)  # can't overflow
+            s = int(daysecondswhole)
+            assert days == int(days)
+            d = int(days)
+        else:
+            daysecondsfrac = 0.0
+            d = days
+        assert isinstance(daysecondsfrac, float)
+        assert abs(daysecondsfrac) <= 1.0
+        assert isinstance(d, int)
+        assert abs(s) <= 24 * 3600
+        # days isn't referenced again before redefinition
+
+        if isinstance(seconds, float):
+            secondsfrac, seconds = _math.modf(seconds)
+            assert seconds == int(seconds)
+            seconds = int(seconds)
+            secondsfrac += daysecondsfrac
+            assert abs(secondsfrac) <= 2.0
+        else:
+            secondsfrac = daysecondsfrac
+        # daysecondsfrac isn't referenced again
+        assert isinstance(secondsfrac, float)
+        assert abs(secondsfrac) <= 2.0
+
+        assert isinstance(seconds, int)
+        days, seconds = divmod(seconds, 24*3600)
+        d += days
+        s += int(seconds)    # can't overflow
+        assert isinstance(s, int)
+        assert abs(s) <= 2 * 24 * 3600
+        # seconds isn't referenced again before redefinition
+
+        usdouble = secondsfrac * 1e6
+        assert abs(usdouble) < 2.1e6    # exact value not critical
+        # secondsfrac isn't referenced again
+
+        if isinstance(microseconds, float):
+            microseconds += usdouble
+            microseconds = round(microseconds, 0)
+            seconds, microseconds = divmod(microseconds, 1e6)
+            assert microseconds == int(microseconds)
+            assert seconds == int(seconds)
+            days, seconds = divmod(seconds, 24.*3600.)
+            assert days == int(days)
+            assert seconds == int(seconds)
+            d += int(days)
+            s += int(seconds)   # can't overflow
+            assert isinstance(s, int)
+            assert abs(s) <= 3 * 24 * 3600
+        else:
+            seconds, microseconds = divmod(microseconds, 1000000)
+            days, seconds = divmod(seconds, 24*3600)
+            d += days
+            s += int(seconds)    # can't overflow
+            assert isinstance(s, int)
+            assert abs(s) <= 3 * 24 * 3600
+            microseconds = float(microseconds)
+            microseconds += usdouble
+            microseconds = round(microseconds, 0)
+        assert abs(s) <= 3 * 24 * 3600
+        assert abs(microseconds) < 3.1e6
+
+        # Just a little bit of carrying possible for microseconds and seconds.
+        assert isinstance(microseconds, float)
+        assert int(microseconds) == microseconds
+        us = int(microseconds)
+        seconds, us = divmod(us, 1000000)
+        s += seconds    # cant't overflow
+        assert isinstance(s, int)
+        days, s = divmod(s, 24*3600)
+        d += days
+
+        assert isinstance(d, int)
+        assert isinstance(s, int) and 0 <= s < 24*3600
+        assert isinstance(us, int) and 0 <= us < 1000000
+
+        self = object.__new__(cls)
+
+        self._days = d
+        self._seconds = s
+        self._microseconds = us
+        if abs(d) > 999999999:
+            raise OverflowError("timedelta # of days is too large: %d" % d)
+
+        return self
+
+    def __repr__(self):
+        if self._microseconds:
+            return "%s(%d, %d, %d)" % ('datetime.' + self.__class__.__name__,
+                                       self._days,
+                                       self._seconds,
+                                       self._microseconds)
+        if self._seconds:
+            return "%s(%d, %d)" % ('datetime.' + self.__class__.__name__,
+                                   self._days,
+                                   self._seconds)
+        return "%s(%d)" % ('datetime.' + self.__class__.__name__, self._days)
+
+    def __str__(self):
+        mm, ss = divmod(self._seconds, 60)
+        hh, mm = divmod(mm, 60)
+        s = "%d:%02d:%02d" % (hh, mm, ss)
+        if self._days:
+            def plural(n):
+                return n, abs(n) != 1 and "s" or ""
+            s = ("%d day%s, " % plural(self._days)) + s
+        if self._microseconds:
+            s = s + ".%06d" % self._microseconds
+        return s
+
+    def total_seconds(self):
+        """Total seconds in the duration."""
+        return ((self.days * 86400 + self.seconds)*10**6 +
+                self.microseconds) / 10**6
+
+    # Read-only field accessors
+    @property
+    def days(self):
+        """days"""
+        return self._days
+
+    @property
+    def seconds(self):
+        """seconds"""
+        return self._seconds
+
+    @property
+    def microseconds(self):
+        """microseconds"""
+        return self._microseconds
+
+    def __add__(self, other):
+        if isinstance(other, timedelta):
+            # for CPython compatibility, we cannot use
+            # our __class__ here, but need a real timedelta
+            return timedelta(self._days + other._days,
+                             self._seconds + other._seconds,
+                             self._microseconds + other._microseconds)
+        return NotImplemented
+
+    __radd__ = __add__
+
+    def __sub__(self, other):
+        if isinstance(other, timedelta):
+            return self + -other
+        return NotImplemented
+
+    def __rsub__(self, other):
+        if isinstance(other, timedelta):
+            return -self + other
+        return NotImplemented
+
+    def __neg__(self):
+        # for CPython compatibility, we cannot use
+        # our __class__ here, but need a real timedelta
+        return timedelta(-self._days,
+                         -self._seconds,
+                         -self._microseconds)
+
+    def __pos__(self):
+        return self
+
+    def __abs__(self):
+        if self._days < 0:
+            return -self
+        else:
+            return self
+
+    def __mul__(self, other):
+        if isinstance(other, int):
+            # for CPython compatibility, we cannot use
+            # our __class__ here, but need a real timedelta
+            return timedelta(self._days * other,
+                             self._seconds * other,
+                             self._microseconds * other)
+        if isinstance(other, float):
+            a, b = other.as_integer_ratio()
+            return self * a / b
+        return NotImplemented
+
+    __rmul__ = __mul__
+
+    def _to_microseconds(self):
+        return ((self._days * (24*3600) + self._seconds) * 1000000 +
+                self._microseconds)
+
+    def __floordiv__(self, other):
+        if not isinstance(other, (int, timedelta)):
+            return NotImplemented
+        usec = self._to_microseconds()
+        if isinstance(other, timedelta):
+            return usec // other._to_microseconds()
+        if isinstance(other, int):
+            return timedelta(0, 0, usec // other)
+
+    def __truediv__(self, other):
+        if not isinstance(other, (int, float, timedelta)):
+            return NotImplemented
+        usec = self._to_microseconds()
+        if isinstance(other, timedelta):
+            return usec / other._to_microseconds()
+        if isinstance(other, int):
+            return timedelta(0, 0, usec / other)
+        if isinstance(other, float):
+            a, b = other.as_integer_ratio()
+            return timedelta(0, 0, b * usec / a)
+
+    def __mod__(self, other):
+        if isinstance(other, timedelta):
+            r = self._to_microseconds() % other._to_microseconds()
+            return timedelta(0, 0, r)
+        return NotImplemented
+
+    def __divmod__(self, other):
+        if isinstance(other, timedelta):
+            q, r = divmod(self._to_microseconds(),
+                          other._to_microseconds())
+            return q, timedelta(0, 0, r)
+        return NotImplemented
+
+    # Comparisons of timedelta objects with other.
+
+    def __eq__(self, other):
+        if isinstance(other, timedelta):
+            return self._cmp(other) == 0
+        else:
+            return False
+
+    def __ne__(self, other):
+        if isinstance(other, timedelta):
+            return self._cmp(other) != 0
+        else:
+            return True
+
+    def __le__(self, other):
+        if isinstance(other, timedelta):
+            return self._cmp(other) <= 0
+        else:
+            _cmperror(self, other)
+
+    def __lt__(self, other):
+        if isinstance(other, timedelta):
+            return self._cmp(other) < 0
+        else:
+            _cmperror(self, other)
+
+    def __ge__(self, other):
+        if isinstance(other, timedelta):
+            return self._cmp(other) >= 0
+        else:
+            _cmperror(self, other)
+
+    def __gt__(self, other):
+        if isinstance(other, timedelta):
+            return self._cmp(other) > 0
+        else:
+            _cmperror(self, other)
+
+    def _cmp(self, other):
+        assert isinstance(other, timedelta)
+        return _cmp(self._getstate(), other._getstate())
+
+    def __hash__(self):
+        return hash(self._getstate())
+
+    def __bool__(self):
+        return (self._days != 0 or
+                self._seconds != 0 or
+                self._microseconds != 0)
+
+    # Pickle support.
+
+    def _getstate(self):
+        return (self._days, self._seconds, self._microseconds)
+
+    def __reduce__(self):
+        return (self.__class__, self._getstate())
+
+timedelta.min = timedelta(-999999999)
+timedelta.max = timedelta(days=999999999, hours=23, minutes=59, seconds=59,
+                          microseconds=999999)
+timedelta.resolution = timedelta(microseconds=1)
+
+class date:
+    """Concrete date type.
+
+    Constructors:
+
+    __new__()
+    fromtimestamp()
+    today()
+    fromordinal()
+
+    Operators:
+
+    __repr__, __str__
+    __cmp__, __hash__
+    __add__, __radd__, __sub__ (add/radd only with timedelta arg)
+
+    Methods:
+
+    timetuple()
+    toordinal()
+    weekday()
+    isoweekday(), isocalendar(), isoformat()
+    ctime()
+    strftime()
+
+    Properties (readonly):
+    year, month, day
+    """
+    __slots__ = '_year', '_month', '_day'
+
+    def __new__(cls, year, month=None, day=None):
+        """Constructor.
+
+        Arguments:
+
+        year, month, day (required, base 1)
+        """
+        if (isinstance(year, bytes) and len(year) == 4 and
+            1 <= year[2] <= 12 and month is None):  # Month is sane
+            # Pickle support
+            self = object.__new__(cls)
+            self.__setstate(year)
+            return self
+        _check_date_fields(year, month, day)
+        self = object.__new__(cls)
+        self._year = year
+        self._month = month
+        self._day = day
+        return self
+
+    # Additional constructors
+
+    @classmethod
+    def fromtimestamp(cls, t):
+        "Construct a date from a POSIX timestamp (like time.time())."
+        y, m, d, hh, mm, ss, weekday, jday, dst = _time.localtime(t)
+        return cls(y, m, d)
+
+    @classmethod
+    def today(cls):
+        "Construct a date from time.time()."
+        t = _time.time()
+        return cls.fromtimestamp(t)
+
+    @classmethod
+    def fromordinal(cls, n):
+        """Contruct a date from a proleptic Gregorian ordinal.
+
+        January 1 of year 1 is day 1.  Only the year, month and day are
+        non-zero in the result.
+        """
+        y, m, d = _ord2ymd(n)
+        return cls(y, m, d)
+
+    # Conversions to string
+
+    def __repr__(self):
+        """Convert to formal string, for repr().
+
+        >>> dt = datetime(2010, 1, 1)
+        >>> repr(dt)
+        'datetime.datetime(2010, 1, 1, 0, 0)'
+
+        >>> dt = datetime(2010, 1, 1, tzinfo=timezone.utc)
+        >>> repr(dt)
+        'datetime.datetime(2010, 1, 1, 0, 0, tzinfo=datetime.timezone.utc)'
+        """
+        return "%s(%d, %d, %d)" % ('datetime.' + self.__class__.__name__,
+                                   self._year,
+                                   self._month,
+                                   self._day)
+    # XXX These shouldn't depend on time.localtime(), because that
+    # clips the usable dates to [1970 .. 2038).  At least ctime() is
+    # easily done without using strftime() -- that's better too because
+    # strftime("%c", ...) is locale specific.
+
+
+    def ctime(self):
+        "Return ctime() style string."
+        weekday = self.toordinal() % 7 or 7
+        return "%s %s %2d 00:00:00 %04d" % (
+            _DAYNAMES[weekday],
+            _MONTHNAMES[self._month],
+            self._day, self._year)
+
+    def strftime(self, fmt):
+        "Format using strftime()."
+        return _wrap_strftime(self, fmt, self.timetuple())
+
+    def __format__(self, fmt):
+        if len(fmt) != 0:
+            return self.strftime(fmt)
+        return str(self)
+
+    def isoformat(self):
+        """Return the date formatted according to ISO.
+
+        This is 'YYYY-MM-DD'.
+
+        References:
+        - http://www.w3.org/TR/NOTE-datetime
+        - http://www.cl.cam.ac.uk/~mgk25/iso-time.html
+        """
+        return "%04d-%02d-%02d" % (self._year, self._month, self._day)
+
+    __str__ = isoformat
+
+    # Read-only field accessors
+    @property
+    def year(self):
+        """year (1-9999)"""
+        return self._year
+
+    @property
+    def month(self):
+        """month (1-12)"""
+        return self._month
+
+    @property
+    def day(self):
+        """day (1-31)"""
+        return self._day
+
+    # Standard conversions, __cmp__, __hash__ (and helpers)
+
+    def timetuple(self):
+        "Return local time tuple compatible with time.localtime()."
+        return _build_struct_time(self._year, self._month, self._day,
+                                  0, 0, 0, -1)
+
+    def toordinal(self):
+        """Return proleptic Gregorian ordinal for the year, month and day.
+
+        January 1 of year 1 is day 1.  Only the year, month and day values
+        contribute to the result.
+        """
+        return _ymd2ord(self._year, self._month, self._day)
+
+    def replace(self, year=None, month=None, day=None):
+        """Return a new date with new values for the specified fields."""
+        if year is None:
+            year = self._year
+        if month is None:
+            month = self._month
+        if day is None:
+            day = self._day
+        _check_date_fields(year, month, day)
+        return date(year, month, day)
+
+    # Comparisons of date objects with other.
+
+    def __eq__(self, other):
+        if isinstance(other, date):
+            return self._cmp(other) == 0
+        return NotImplemented
+
+    def __ne__(self, other):
+        if isinstance(other, date):
+            return self._cmp(other) != 0
+        return NotImplemented
+
+    def __le__(self, other):
+        if isinstance(other, date):
+            return self._cmp(other) <= 0
+        return NotImplemented
+
+    def __lt__(self, other):
+        if isinstance(other, date):
+            return self._cmp(other) < 0
+        return NotImplemented
+
+    def __ge__(self, other):
+        if isinstance(other, date):
+            return self._cmp(other) >= 0
+        return NotImplemented
+
+    def __gt__(self, other):
+        if isinstance(other, date):
+            return self._cmp(other) > 0
+        return NotImplemented
+
+    def _cmp(self, other):
+        assert isinstance(other, date)
+        y, m, d = self._year, self._month, self._day
+        y2, m2, d2 = other._year, other._month, other._day
+        return _cmp((y, m, d), (y2, m2, d2))
+
+    def __hash__(self):
+        "Hash."
+        return hash(self._getstate())
+
+    # Computations
+
+    def __add__(self, other):
+        "Add a date to a timedelta."
+        if isinstance(other, timedelta):
+            o = self.toordinal() + other.days
+            if 0 < o <= _MAXORDINAL:
+                return date.fromordinal(o)
+            raise OverflowError("result out of range")
+        return NotImplemented
+
+    __radd__ = __add__
+
+    def __sub__(self, other):
+        """Subtract two dates, or a date and a timedelta."""
+        if isinstance(other, timedelta):
+            return self + timedelta(-other.days)
+        if isinstance(other, date):
+            days1 = self.toordinal()
+            days2 = other.toordinal()
+            return timedelta(days1 - days2)
+        return NotImplemented
+
+    def weekday(self):
+        "Return day of the week, where Monday == 0 ... Sunday == 6."
+        return (self.toordinal() + 6) % 7
+
+    # Day-of-the-week and week-of-the-year, according to ISO
+
+    def isoweekday(self):
+        "Return day of the week, where Monday == 1 ... Sunday == 7."
+        # 1-Jan-0001 is a Monday
+        return self.toordinal() % 7 or 7
+
+    def isocalendar(self):
+        """Return a 3-tuple containing ISO year, week number, and weekday.
+
+        The first ISO week of the year is the (Mon-Sun) week
+        containing the year's first Thursday; everything else derives
+        from that.
+
+        The first week is 1; Monday is 1 ... Sunday is 7.
+
+        ISO calendar algorithm taken from
+        http://www.phys.uu.nl/~vgent/calendar/isocalendar.htm
+        """
+        year = self._year
+        week1monday = _isoweek1monday(year)
+        today = _ymd2ord(self._year, self._month, self._day)
+        # Internally, week and day have origin 0
+        week, day = divmod(today - week1monday, 7)
+        if week < 0:
+            year -= 1
+            week1monday = _isoweek1monday(year)
+            week, day = divmod(today - week1monday, 7)
+        elif week >= 52:
+            if today >= _isoweek1monday(year+1):
+                year += 1
+                week = 0
+        return year, week+1, day+1
+
+    # Pickle support.
+
+    def _getstate(self):
+        yhi, ylo = divmod(self._year, 256)
+        return bytes([yhi, ylo, self._month, self._day]),
+
+    def __setstate(self, string):
+        if len(string) != 4 or not (1 <= string[2] <= 12):
+            raise TypeError("not enough arguments")
+        yhi, ylo, self._month, self._day = string
+        self._year = yhi * 256 + ylo
+
+    def __reduce__(self):
+        return (self.__class__, self._getstate())
+
+_date_class = date  # so functions w/ args named "date" can get at the class
+
+date.min = date(1, 1, 1)
+date.max = date(9999, 12, 31)
+date.resolution = timedelta(days=1)
+
+class tzinfo:
+    """Abstract base class for time zone info classes.
+
+    Subclasses must override the name(), utcoffset() and dst() methods.
+    """
+    __slots__ = ()
+    def tzname(self, dt):
+        "datetime -> string name of time zone."
+        raise NotImplementedError("tzinfo subclass must override tzname()")
+
+    def utcoffset(self, dt):
+        "datetime -> minutes east of UTC (negative for west of UTC)"
+        raise NotImplementedError("tzinfo subclass must override utcoffset()")
+
+    def dst(self, dt):
+        """datetime -> DST offset in minutes east of UTC.
+
+        Return 0 if DST not in effect.  utcoffset() must include the DST
+        offset.
+        """
+        raise NotImplementedError("tzinfo subclass must override dst()")
+
+    def fromutc(self, dt):
+        "datetime in UTC -> datetime in local time."
+
+        if not isinstance(dt, datetime):
+            raise TypeError("fromutc() requires a datetime argument")
+        if dt.tzinfo is not self:
+            raise ValueError("dt.tzinfo is not self")
+
+        dtoff = dt.utcoffset()
+        if dtoff is None:
+            raise ValueError("fromutc() requires a non-None utcoffset() "
+                             "result")
+
+        # See the long comment block at the end of this file for an
+        # explanation of this algorithm.
+        dtdst = dt.dst()
+        if dtdst is None:
+            raise ValueError("fromutc() requires a non-None dst() result")
+        delta = dtoff - dtdst
+        if delta:
+            dt += delta
+            dtdst = dt.dst()
+            if dtdst is None:
+                raise ValueError("fromutc(): dt.dst gave inconsistent "
+                                 "results; cannot convert")
+        return dt + dtdst
+
+    # Pickle support.
+
+    def __reduce__(self):
+        getinitargs = getattr(self, "__getinitargs__", None)
+        if getinitargs:
+            args = getinitargs()
+        else:
+            args = ()
+        getstate = getattr(self, "__getstate__", None)
+        if getstate:
+            state = getstate()
+        else:
+            state = getattr(self, "__dict__", None) or None
+        if state is None:
+            return (self.__class__, args)
+        else:
+            return (self.__class__, args, state)
+
+_tzinfo_class = tzinfo
+
+class time:
+    """Time with time zone.
+
+    Constructors:
+
+    __new__()
+
+    Operators:
+
+    __repr__, __str__
+    __cmp__, __hash__
+
+    Methods:
+
+    strftime()
+    isoformat()
+    utcoffset()
+    tzname()
+    dst()
+
+    Properties (readonly):
+    hour, minute, second, microsecond, tzinfo
+    """
+
+    def __new__(cls, hour=0, minute=0, second=0, microsecond=0, tzinfo=None):
+        """Constructor.
+
+        Arguments:
+
+        hour, minute (required)
+        second, microsecond (default to zero)
+        tzinfo (default to None)
+        """
+        self = object.__new__(cls)
+        if isinstance(hour, bytes) and len(hour) == 6:
+            # Pickle support
+            self.__setstate(hour, minute or None)
+            return self
+        _check_tzinfo_arg(tzinfo)
+        _check_time_fields(hour, minute, second, microsecond)
+        self._hour = hour
+        self._minute = minute
+        self._second = second
+        self._microsecond = microsecond
+        self._tzinfo = tzinfo
+        return self
+
+    # Read-only field accessors
+    @property
+    def hour(self):
+        """hour (0-23)"""
+        return self._hour
+
+    @property
+    def minute(self):
+        """minute (0-59)"""
+        return self._minute
+
+    @property
+    def second(self):
+        """second (0-59)"""
+        return self._second
+
+    @property
+    def microsecond(self):
+        """microsecond (0-999999)"""
+        return self._microsecond
+
+    @property
+    def tzinfo(self):
+        """timezone info object"""
+        return self._tzinfo
+
+    # Standard conversions, __hash__ (and helpers)
+
+    # Comparisons of time objects with other.
+
+    def __eq__(self, other):
+        if isinstance(other, time):
+            return self._cmp(other) == 0
+        else:
+            return False
+
+    def __ne__(self, other):
+        if isinstance(other, time):
+            return self._cmp(other) != 0
+        else:
+            return True
+
+    def __le__(self, other):
+        if isinstance(other, time):
+            return self._cmp(other) <= 0
+        else:
+            _cmperror(self, other)
+
+    def __lt__(self, other):
+        if isinstance(other, time):
+            return self._cmp(other) < 0
+        else:
+            _cmperror(self, other)
+
+    def __ge__(self, other):
+        if isinstance(other, time):
+            return self._cmp(other) >= 0
+        else:
+            _cmperror(self, other)
+
+    def __gt__(self, other):
+        if isinstance(other, time):
+            return self._cmp(other) > 0
+        else:
+            _cmperror(self, other)
+
+    def _cmp(self, other):
+        assert isinstance(other, time)
+        mytz = self._tzinfo
+        ottz = other._tzinfo
+        myoff = otoff = None
+
+        if mytz is ottz:
+            base_compare = True
+        else:
+            myoff = self.utcoffset()
+            otoff = other.utcoffset()
+            base_compare = myoff == otoff
+
+        if base_compare:
+            return _cmp((self._hour, self._minute, self._second,
+                         self._microsecond),
+                       (other._hour, other._minute, other._second,
+                        other._microsecond))
+        if myoff is None or otoff is None:
+            raise TypeError("cannot compare naive and aware times")
+        myhhmm = self._hour * 60 + self._minute - myoff//timedelta(minutes=1)
+        othhmm = other._hour * 60 + other._minute - otoff//timedelta(minutes=1)
+        return _cmp((myhhmm, self._second, self._microsecond),
+                    (othhmm, other._second, other._microsecond))
+
+    def __hash__(self):
+        """Hash."""
+        tzoff = self.utcoffset()
+        if not tzoff: # zero or None
+            return hash(self._getstate()[0])
+        h, m = divmod(timedelta(hours=self.hour, minutes=self.minute) - tzoff,
+                      timedelta(hours=1))
+        assert not m % timedelta(minutes=1), "whole minute"
+        m //= timedelta(minutes=1)
+        if 0 <= h < 24:
+            return hash(time(h, m, self.second, self.microsecond))
+        return hash((h, m, self.second, self.microsecond))
+
+    # Conversion to string
+
+    def _tzstr(self, sep=":"):
+        """Return formatted timezone offset (+xx:xx) or None."""
+        off = self.utcoffset()
+        if off is not None:
+            if off.days < 0:
+                sign = "-"
+                off = -off
+            else:
+                sign = "+"
+            hh, mm = divmod(off, timedelta(hours=1))
+            assert not mm % timedelta(minutes=1), "whole minute"
+            mm //= timedelta(minutes=1)
+            assert 0 <= hh < 24
+            off = "%s%02d%s%02d" % (sign, hh, sep, mm)
+        return off
+
+    def __repr__(self):
+        """Convert to formal string, for repr()."""
+        if self._microsecond != 0:
+            s = ", %d, %d" % (self._second, self._microsecond)
+        elif self._second != 0:
+            s = ", %d" % self._second
+        else:
+            s = ""
+        s= "%s(%d, %d%s)" % ('datetime.' + self.__class__.__name__,
+                             self._hour, self._minute, s)
+        if self._tzinfo is not None:
+            assert s[-1:] == ")"
+            s = s[:-1] + ", tzinfo=%r" % self._tzinfo + ")"
+        return s
+
+    def isoformat(self):
+        """Return the time formatted according to ISO.
+
+        This is 'HH:MM:SS.mmmmmm+zz:zz', or 'HH:MM:SS+zz:zz' if
+        self.microsecond == 0.
+        """
+        s = _format_time(self._hour, self._minute, self._second,
+                         self._microsecond)
+        tz = self._tzstr()
+        if tz:
+            s += tz
+        return s
+
+    __str__ = isoformat
+
+    def strftime(self, fmt):
+        """Format using strftime().  The date part of the timestamp passed
+        to underlying strftime should not be used.
+        """
+        # The year must be >= 1900 else Python's strftime implementation
+        # can raise a bogus exception.
+        timetuple = (1900, 1, 1,
+                     self._hour, self._minute, self._second,
+                     0, 1, -1)
+        return _wrap_strftime(self, fmt, timetuple)
+
+    def __format__(self, fmt):
+        if len(fmt) != 0:
+            return self.strftime(fmt)
+        return str(self)
+
+    # Timezone functions
+
+    def utcoffset(self):
+        """Return the timezone offset in minutes east of UTC (negative west of
+        UTC)."""
+        if self._tzinfo is None:
+            return None
+        offset = self._tzinfo.utcoffset(None)
+        _check_utc_offset("utcoffset", offset)
+        return offset
+
+    def tzname(self):
+        """Return the timezone name.
+
+        Note that the name is 100% informational -- there's no requirement that
+        it mean anything in particular. For example, "GMT", "UTC", "-500",
+        "-5:00", "EDT", "US/Eastern", "America/New York" are all valid replies.
+        """
+        if self._tzinfo is None:
+            return None
+        name = self._tzinfo.tzname(None)
+        _check_tzname(name)
+        return name
+
+    def dst(self):
+        """Return 0 if DST is not in effect, or the DST offset (in minutes
+        eastward) if DST is in effect.
+
+        This is purely informational; the DST offset has already been added to
+        the UTC offset returned by utcoffset() if applicable, so there's no
+        need to consult dst() unless you're interested in displaying the DST
+        info.
+        """
+        if self._tzinfo is None:
+            return None
+        offset = self._tzinfo.dst(None)
+        _check_utc_offset("dst", offset)
+        return offset
+
+    def replace(self, hour=None, minute=None, second=None, microsecond=None,
+                tzinfo=True):
+        """Return a new time with new values for the specified fields."""
+        if hour is None:
+            hour = self.hour
+        if minute is None:
+            minute = self.minute
+        if second is None:
+            second = self.second
+        if microsecond is None:
+            microsecond = self.microsecond
+        if tzinfo is True:
+            tzinfo = self.tzinfo
+        _check_time_fields(hour, minute, second, microsecond)
+        _check_tzinfo_arg(tzinfo)
+        return time(hour, minute, second, microsecond, tzinfo)
+
+    def __bool__(self):
+        if self.second or self.microsecond:
+            return True
+        offset = self.utcoffset() or timedelta(0)
+        return timedelta(hours=self.hour, minutes=self.minute) != offset
+
+    # Pickle support.
+
+    def _getstate(self):
+        us2, us3 = divmod(self._microsecond, 256)
+        us1, us2 = divmod(us2, 256)
+        basestate = bytes([self._hour, self._minute, self._second,
+                           us1, us2, us3])
+        if self._tzinfo is None:
+            return (basestate,)
+        else:
+            return (basestate, self._tzinfo)
+
+    def __setstate(self, string, tzinfo):
+        if len(string) != 6 or string[0] >= 24:
+            raise TypeError("an integer is required")
+        (self._hour, self._minute, self._second,
+         us1, us2, us3) = string
+        self._microsecond = (((us1 << 8) | us2) << 8) | us3
+        if tzinfo is None or isinstance(tzinfo, _tzinfo_class):
+            self._tzinfo = tzinfo
+        else:
+            raise TypeError("bad tzinfo state arg %r" % tzinfo)
+
+    def __reduce__(self):
+        return (time, self._getstate())
+
+_time_class = time  # so functions w/ args named "time" can get at the class
+
+time.min = time(0, 0, 0)
+time.max = time(23, 59, 59, 999999)
+time.resolution = timedelta(microseconds=1)
+
+class datetime(date):
+    """datetime(year, month, day[, hour[, minute[, second[, microsecond[,tzinfo]]]]])
+
+    The year, month and day arguments are required. tzinfo may be None, or an
+    instance of a tzinfo subclass. The remaining arguments may be ints or longs.
+    """
+
+    __slots__ = date.__slots__ + (
+        '_hour', '_minute', '_second',
+        '_microsecond', '_tzinfo')
+    def __new__(cls, year, month=None, day=None, hour=0, minute=0, second=0,
+                microsecond=0, tzinfo=None):
+        if isinstance(year, bytes) and len(year) == 10:
+            # Pickle support
+            self = date.__new__(cls, year[:4])
+            self.__setstate(year, month)
+            return self
+        _check_tzinfo_arg(tzinfo)
+        _check_time_fields(hour, minute, second, microsecond)
+        self = date.__new__(cls, year, month, day)
+        self._hour = hour
+        self._minute = minute
+        self._second = second
+        self._microsecond = microsecond
+        self._tzinfo = tzinfo
+        return self
+
+    # Read-only field accessors
+    @property
+    def hour(self):
+        """hour (0-23)"""
+        return self._hour
+
+    @property
+    def minute(self):
+        """minute (0-59)"""
+        return self._minute
+
+    @property
+    def second(self):
+        """second (0-59)"""
+        return self._second
+
+    @property
+    def microsecond(self):
+        """microsecond (0-999999)"""
+        return self._microsecond
+
+    @property
+    def tzinfo(self):
+        """timezone info object"""
+        return self._tzinfo
+
+    @classmethod
+    def fromtimestamp(cls, t, tz=None):
+        """Construct a datetime from a POSIX timestamp (like time.time()).
+
+        A timezone info object may be passed in as well.
+        """
+
+        _check_tzinfo_arg(tz)
+        if tz is None:
+            converter = _time.localtime
+        else:
+            converter = _time.gmtime
+        if 1 - (t % 1.0) < 0.000001:
+            t = float(int(t)) + 1
+        if t < 0:
+            t -= 1
+        y, m, d, hh, mm, ss, weekday, jday, dst = converter(t)
+        us = int((t % 1.0) * 1000000)
+        ss = min(ss, 59)    # clamp out leap seconds if the platform has them
+        result = cls(y, m, d, hh, mm, ss, us, tz)
+        if tz is not None:
+            result = tz.fromutc(result)
+        return result
+
+    @classmethod
+    def utcfromtimestamp(cls, t):
+        "Construct a UTC datetime from a POSIX timestamp (like time.time())."
+        if 1 - (t % 1.0) < 0.000001:
+            t = float(int(t)) + 1
+        if t < 0:
+            t -= 1
+        y, m, d, hh, mm, ss, weekday, jday, dst = _time.gmtime(t)
+        us = int((t % 1.0) * 1000000)
+        ss = min(ss, 59)    # clamp out leap seconds if the platform has them
+        return cls(y, m, d, hh, mm, ss, us)
+
+    # XXX This is supposed to do better than we *can* do by using time.time(),
+    # XXX if the platform supports a more accurate way.  The C implementation
+    # XXX uses gettimeofday on platforms that have it, but that isn't
+    # XXX available from Python.  So now() may return different results
+    # XXX across the implementations.
+    @classmethod
+    def now(cls, tz=None):
+        "Construct a datetime from time.time() and optional time zone info."
+        t = _time.time()
+        return cls.fromtimestamp(t, tz)
+
+    @classmethod
+    def utcnow(cls):
+        "Construct a UTC datetime from time.time()."
+        t = _time.time()
+        return cls.utcfromtimestamp(t)
+
+    @classmethod
+    def combine(cls, date, time):
+        "Construct a datetime from a given date and a given time."
+        if not isinstance(date, _date_class):
+            raise TypeError("date argument must be a date instance")
+        if not isinstance(time, _time_class):
+            raise TypeError("time argument must be a time instance")
+        return cls(date.year, date.month, date.day,
+                   time.hour, time.minute, time.second, time.microsecond,
+                   time.tzinfo)
+
+    def timetuple(self):
+        "Return local time tuple compatible with time.localtime()."
+        dst = self.dst()
+        if dst is None:
+            dst = -1
+        elif dst:
+            dst = 1
+        else:
+            dst = 0
+        return _build_struct_time(self.year, self.month, self.day,
+                                  self.hour, self.minute, self.second,
+                                  dst)
+
+    def utctimetuple(self):
+        "Return UTC time tuple compatible with time.gmtime()."
+        offset = self.utcoffset()
+        if offset:
+            self -= offset
+        y, m, d = self.year, self.month, self.day
+        hh, mm, ss = self.hour, self.minute, self.second
+        return _build_struct_time(y, m, d, hh, mm, ss, 0)
+
+    def date(self):
+        "Return the date part."
+        return date(self._year, self._month, self._day)
+
+    def time(self):
+        "Return the time part, with tzinfo None."
+        return time(self.hour, self.minute, self.second, self.microsecond)
+
+    def timetz(self):
+        "Return the time part, with same tzinfo."
+        return time(self.hour, self.minute, self.second, self.microsecond,
+                    self._tzinfo)
+
+    def replace(self, year=None, month=None, day=None, hour=None,
+                minute=None, second=None, microsecond=None, tzinfo=True):
+        """Return a new datetime with new values for the specified fields."""
+        if year is None:
+            year = self.year
+        if month is None:
+            month = self.month
+        if day is None:
+            day = self.day
+        if hour is None:
+            hour = self.hour
+        if minute is None:
+            minute = self.minute
+        if second is None:
+            second = self.second
+        if microsecond is None:
+            microsecond = self.microsecond
+        if tzinfo is True:
+            tzinfo = self.tzinfo
+        _check_date_fields(year, month, day)
+        _check_time_fields(hour, minute, second, microsecond)
+        _check_tzinfo_arg(tzinfo)
+        return datetime(year, month, day, hour, minute, second,
+                          microsecond, tzinfo)
+
+    def astimezone(self, tz):
+        if not isinstance(tz, tzinfo):
+            raise TypeError("tz argument must be an instance of tzinfo")
+
+        mytz = self.tzinfo
+        if mytz is None:
+            raise ValueError("astimezone() requires an aware datetime")
+
+        if tz is mytz:
+            return self
+
+        # Convert self to UTC, and attach the new time zone object.
+        myoffset = self.utcoffset()
+        if myoffset is None:
+            raise ValueError("astimezone() requires an aware datetime")
+        utc = (self - myoffset).replace(tzinfo=tz)
+
+        # Convert from UTC to tz's local time.
+        return tz.fromutc(utc)
+
+    # Ways to produce a string.
+
+    def ctime(self):
+        "Return ctime() style string."
+        weekday = self.toordinal() % 7 or 7
+        return "%s %s %2d %02d:%02d:%02d %04d" % (
+            _DAYNAMES[weekday],
+            _MONTHNAMES[self._month],
+            self._day,
+            self._hour, self._minute, self._second,
+            self._year)
+
+    def isoformat(self, sep='T'):
+        """Return the time formatted according to ISO.
+
+        This is 'YYYY-MM-DD HH:MM:SS.mmmmmm', or 'YYYY-MM-DD HH:MM:SS' if
+        self.microsecond == 0.
+
+        If self.tzinfo is not None, the UTC offset is also attached, giving
+        'YYYY-MM-DD HH:MM:SS.mmmmmm+HH:MM' or 'YYYY-MM-DD HH:MM:SS+HH:MM'.
+
+        Optional argument sep specifies the separator between date and
+        time, default 'T'.
+        """
+        s = ("%04d-%02d-%02d%c" % (self._year, self._month, self._day,
+                                  sep) +
+                _format_time(self._hour, self._minute, self._second,
+                             self._microsecond))
+        off = self.utcoffset()
+        if off is not None:
+            if off.days < 0:
+                sign = "-"
+                off = -off
+            else:
+                sign = "+"
+            hh, mm = divmod(off, timedelta(hours=1))
+            assert not mm % timedelta(minutes=1), "whole minute"
+            mm //= timedelta(minutes=1)
+            s += "%s%02d:%02d" % (sign, hh, mm)
+        return s
+
+    def __repr__(self):
+        """Convert to formal string, for repr()."""
+        L = [self._year, self._month, self._day, # These are never zero
+             self._hour, self._minute, self._second, self._microsecond]
+        if L[-1] == 0:
+            del L[-1]
+        if L[-1] == 0:
+            del L[-1]
+        s = ", ".join(map(str, L))
+        s = "%s(%s)" % ('datetime.' + self.__class__.__name__, s)
+        if self._tzinfo is not None:
+            assert s[-1:] == ")"
+            s = s[:-1] + ", tzinfo=%r" % self._tzinfo + ")"
+        return s
+
+    def __str__(self):
+        "Convert to string, for str()."
+        return self.isoformat(sep=' ')
+
+    @classmethod
+    def strptime(cls, date_string, format):
+        'string, format -> new datetime parsed from a string (like time.strptime()).'
+        import _strptime
+        return _strptime._strptime_datetime(cls, date_string, format)
+
+    def utcoffset(self):
+        """Return the timezone offset in minutes east of UTC (negative west of
+        UTC)."""
+        if self._tzinfo is None:
+            return None
+        offset = self._tzinfo.utcoffset(self)
+        _check_utc_offset("utcoffset", offset)
+        return offset
+
+    def tzname(self):
+        """Return the timezone name.
+
+        Note that the name is 100% informational -- there's no requirement that
+        it mean anything in particular. For example, "GMT", "UTC", "-500",
+        "-5:00", "EDT", "US/Eastern", "America/New York" are all valid replies.
+        """
+        name = _call_tzinfo_method(self._tzinfo, "tzname", self)
+        _check_tzname(name)
+        return name
+
+    def dst(self):
+        """Return 0 if DST is not in effect, or the DST offset (in minutes
+        eastward) if DST is in effect.
+
+        This is purely informational; the DST offset has already been added to
+        the UTC offset returned by utcoffset() if applicable, so there's no
+        need to consult dst() unless you're interested in displaying the DST
+        info.
+        """
+        if self._tzinfo is None:
+            return None
+        offset = self._tzinfo.dst(self)
+        _check_utc_offset("dst", offset)
+        return offset
+
+    # Comparisons of datetime objects with other.
+
+    def __eq__(self, other):
+        if isinstance(other, datetime):
+            return self._cmp(other) == 0
+        elif not isinstance(other, date):
+            return NotImplemented
+        else:
+            return False
+
+    def __ne__(self, other):
+        if isinstance(other, datetime):
+            return self._cmp(other) != 0
+        elif not isinstance(other, date):
+            return NotImplemented
+        else:
+            return True
+
+    def __le__(self, other):
+        if isinstance(other, datetime):
+            return self._cmp(other) <= 0
+        elif not isinstance(other, date):
+            return NotImplemented
+        else:
+            _cmperror(self, other)
+
+    def __lt__(self, other):
+        if isinstance(other, datetime):
+            return self._cmp(other) < 0
+        elif not isinstance(other, date):
+            return NotImplemented
+        else:
+            _cmperror(self, other)
+
+    def __ge__(self, other):
+        if isinstance(other, datetime):
+            return self._cmp(other) >= 0
+        elif not isinstance(other, date):
+            return NotImplemented
+        else:
+            _cmperror(self, other)
+
+    def __gt__(self, other):
+        if isinstance(other, datetime):
+            return self._cmp(other) > 0
+        elif not isinstance(other, date):
+            return NotImplemented
+        else:
+            _cmperror(self, other)
+
+    def _cmp(self, other):
+        assert isinstance(other, datetime)
+        mytz = self._tzinfo
+        ottz = other._tzinfo
+        myoff = otoff = None
+
+        if mytz is ottz:
+            base_compare = True
+        else:
+            if mytz is not None:
+                myoff = self.utcoffset()
+            if ottz is not None:
+                otoff = other.utcoffset()
+            base_compare = myoff == otoff
+
+        if base_compare:
+            return _cmp((self._year, self._month, self._day,
+                         self._hour, self._minute, self._second,
+                         self._microsecond),
+                       (other._year, other._month, other._day,
+                        other._hour, other._minute, other._second,
+                        other._microsecond))
+        if myoff is None or otoff is None:
+            raise TypeError("cannot compare naive and aware datetimes")
+        # XXX What follows could be done more efficiently...
+        diff = self - other     # this will take offsets into account
+        if diff.days < 0:
+            return -1
+        return diff and 1 or 0
+
+    def __add__(self, other):
+        "Add a datetime and a timedelta."
+        if not isinstance(other, timedelta):
+            return NotImplemented
+        delta = timedelta(self.toordinal(),
+                          hours=self._hour,
+                          minutes=self._minute,
+                          seconds=self._second,
+                          microseconds=self._microsecond)
+        delta += other
+        hour, rem = divmod(delta.seconds, 3600)
+        minute, second = divmod(rem, 60)
+        if 0 < delta.days <= _MAXORDINAL:
+            return datetime.combine(date.fromordinal(delta.days),
+                                    time(hour, minute, second,
+                                         delta.microseconds,
+                                         tzinfo=self._tzinfo))
+        raise OverflowError("result out of range")
+
+    __radd__ = __add__
+
+    def __sub__(self, other):
+        "Subtract two datetimes, or a datetime and a timedelta."
+        if not isinstance(other, datetime):
+            if isinstance(other, timedelta):
+                return self + -other
+            return NotImplemented
+
+        days1 = self.toordinal()
+        days2 = other.toordinal()
+        secs1 = self._second + self._minute * 60 + self._hour * 3600
+        secs2 = other._second + other._minute * 60 + other._hour * 3600
+        base = timedelta(days1 - days2,
+                         secs1 - secs2,
+                         self._microsecond - other._microsecond)
+        if self._tzinfo is other._tzinfo:
+            return base
+        myoff = self.utcoffset()
+        otoff = other.utcoffset()
+        if myoff == otoff:
+            return base
+        if myoff is None or otoff is None:
+            raise TypeError("cannot mix naive and timezone-aware time")
+        return base + otoff - myoff
+
+    def __hash__(self):
+        tzoff = self.utcoffset()
+        if tzoff is None:
+            return hash(self._getstate()[0])
+        days = _ymd2ord(self.year, self.month, self.day)
+        seconds = self.hour * 3600 + self.minute * 60 + self.second
+        return hash(timedelta(days, seconds, self.microsecond) - tzoff)
+
+    # Pickle support.
+
+    def _getstate(self):
+        yhi, ylo = divmod(self._year, 256)
+        us2, us3 = divmod(self._microsecond, 256)
+        us1, us2 = divmod(us2, 256)
+        basestate = bytes([yhi, ylo, self._month, self._day,
+                           self._hour, self._minute, self._second,
+                           us1, us2, us3])
+        if self._tzinfo is None:
+            return (basestate,)
+        else:
+            return (basestate, self._tzinfo)
+
+    def __setstate(self, string, tzinfo):
+        (yhi, ylo, self._month, self._day, self._hour,
+         self._minute, self._second, us1, us2, us3) = string
+        self._year = yhi * 256 + ylo
+        self._microsecond = (((us1 << 8) | us2) << 8) | us3
+        if tzinfo is None or isinstance(tzinfo, _tzinfo_class):
+            self._tzinfo = tzinfo
+        else:
+            raise TypeError("bad tzinfo state arg %r" % tzinfo)
+
+    def __reduce__(self):
+        return (self.__class__, self._getstate())
+
+
+datetime.min = datetime(1, 1, 1)
+datetime.max = datetime(9999, 12, 31, 23, 59, 59, 999999)
+datetime.resolution = timedelta(microseconds=1)
+
+
+def _isoweek1monday(year):
+    # Helper to calculate the day number of the Monday starting week 1
+    # XXX This could be done more efficiently
+    THURSDAY = 3
+    firstday = _ymd2ord(year, 1, 1)
+    firstweekday = (firstday + 6) % 7 # See weekday() above
+    week1monday = firstday - firstweekday
+    if firstweekday > THURSDAY:
+        week1monday += 7
+    return week1monday
+
+class timezone(tzinfo):
+    __slots__ = '_offset', '_name'
+
+    # Sentinel value to disallow None
+    _Omitted = object()
+    def __init__(self, offset, name=_Omitted):
+        if name is self._Omitted:
+            name = None
+        elif not isinstance(name, str):
+            raise TypeError("name must be a string")
+        if isinstance(offset, timedelta):
+            if self._minoffset <= offset <= self._maxoffset:
+                if (offset.microseconds != 0 or
+                    offset.seconds % 60 != 0):
+                    raise ValueError("offset must be whole"
+                                    " number of minutes")
+                self._offset = offset
+            else:
+                raise ValueError("offset out of range")
+        else:
+            raise TypeError("offset must be timedelta")
+
+        self._name = name
+
+    def __getinitargs__(self):
+        """pickle support"""
+        if self._name is None:
+            return (self._offset,)
+        return (self._offset, self._name)
+
+    def __eq__(self, other):
+        return self._offset == other._offset
+
+    def __hash__(self):
+        return hash(self._offset)
+
+    def __repr__(self):
+        """Convert to formal string, for repr().
+
+        >>> tz = timezone.utc
+        >>> repr(tz)
+        'datetime.timezone.utc'
+        >>> tz = timezone(timedelta(hours=-5), 'EST')
+        >>> repr(tz)
+        "datetime.timezone(datetime.timedelta(-1, 68400), 'EST')"
+        """
+        if self is self.utc:
+            return 'datetime.timezone.utc'
+        if self._name is None:
+            return "%s(%r)" % ('datetime.' + self.__class__.__name__,
+                               self._offset)
+        return "%s(%r, %r)" % ('datetime.' + self.__class__.__name__,
+                               self._offset, self._name)
+
+    def __str__(self):
+        return self.tzname(None)
+
+    def utcoffset(self, dt):
+        if isinstance(dt, datetime) or dt is None:
+            return self._offset
+        raise TypeError("utcoffset() argument must be a datetime instance"
+                        " or None")
+
+    def tzname(self, dt):
+        if isinstance(dt, datetime) or dt is None:
+            if self._name is None:
+                return self._name_from_offset(self._offset)
+            return self._name
+        raise TypeError("tzname() argument must be a datetime instance"
+                        " or None")
+
+    def dst(self, dt):
+        if isinstance(dt, datetime) or dt is None:
+            return None
+        raise TypeError("dst() argument must be a datetime instance"
+                        " or None")
+
+    def fromutc(self, dt):
+        if isinstance(dt, datetime):
+            if dt.tzinfo is not self:
+                raise ValueError("fromutc: dt.tzinfo "
+                                 "is not self")
+            return dt + self._offset
+        raise TypeError("fromutc() argument must be a datetime instance"
+                        " or None")
+
+    _maxoffset = timedelta(hours=23, minutes=59)
+    _minoffset = -_maxoffset
+
+    @staticmethod
+    def _name_from_offset(delta):
+        if delta < timedelta(0):
+            sign = '-'
+            delta = -delta
+        else:
+            sign = '+'
+        hours, rest = divmod(delta, timedelta(hours=1))
+        minutes = rest // timedelta(minutes=1)
+        return 'UTC{}{:02d}:{:02d}'.format(sign, hours, minutes)
+
+timezone.utc = timezone(timedelta(0))
+timezone.min = timezone(timezone._minoffset)
+timezone.max = timezone(timezone._maxoffset)
+
+"""
+Some time zone algebra.  For a datetime x, let
+    x.n = x stripped of its timezone -- its naive time.
+    x.o = x.utcoffset(), and assuming that doesn't raise an exception or
+          return None
+    x.d = x.dst(), and assuming that doesn't raise an exception or
+          return None
+    x.s = x's standard offset, x.o - x.d
+
+Now some derived rules, where k is a duration (timedelta).
+
+1. x.o = x.s + x.d
+   This follows from the definition of x.s.
+
+2. If x and y have the same tzinfo member, x.s = y.s.
+   This is actually a requirement, an assumption we need to make about
+   sane tzinfo classes.
+
+3. The naive UTC time corresponding to x is x.n - x.o.
+   This is again a requirement for a sane tzinfo class.
+
+4. (x+k).s = x.s
+   This follows from #2, and that datimetimetz+timedelta preserves tzinfo.
+
+5. (x+k).n = x.n + k
+   Again follows from how arithmetic is defined.
+
+Now we can explain tz.fromutc(x).  Let's assume it's an interesting case
+(meaning that the various tzinfo methods exist, and don't blow up or return
+None when called).
+
+The function wants to return a datetime y with timezone tz, equivalent to x.
+x is already in UTC.
+
+By #3, we want
+
+    y.n - y.o = x.n                             [1]
+
+The algorithm starts by attaching tz to x.n, and calling that y.  So
+x.n = y.n at the start.  Then it wants to add a duration k to y, so that [1]
+becomes true; in effect, we want to solve [2] for k:
+
+   (y+k).n - (y+k).o = x.n                      [2]
+
+By #1, this is the same as
+
+   (y+k).n - ((y+k).s + (y+k).d) = x.n          [3]
+
+By #5, (y+k).n = y.n + k, which equals x.n + k because x.n=y.n at the start.
+Substituting that into [3],
+
+   x.n + k - (y+k).s - (y+k).d = x.n; the x.n terms cancel, leaving
+   k - (y+k).s - (y+k).d = 0; rearranging,
+   k = (y+k).s - (y+k).d; by #4, (y+k).s == y.s, so
+   k = y.s - (y+k).d
+
+On the RHS, (y+k).d can't be computed directly, but y.s can be, and we
+approximate k by ignoring the (y+k).d term at first.  Note that k can't be
+very large, since all offset-returning methods return a duration of magnitude
+less than 24 hours.  For that reason, if y is firmly in std time, (y+k).d must
+be 0, so ignoring it has no consequence then.
+
+In any case, the new value is
+
+    z = y + y.s                                 [4]
+
+It's helpful to step back at look at [4] from a higher level:  it's simply
+mapping from UTC to tz's standard time.
+
+At this point, if
+
+    z.n - z.o = x.n                             [5]
+
+we have an equivalent time, and are almost done.  The insecurity here is
+at the start of daylight time.  Picture US Eastern for concreteness.  The wall
+time jumps from 1:59 to 3:00, and wall hours of the form 2:MM don't make good
+sense then.  The docs ask that an Eastern tzinfo class consider such a time to
+be EDT (because it's "after 2"), which is a redundant spelling of 1:MM EST
+on the day DST starts.  We want to return the 1:MM EST spelling because that's
+the only spelling that makes sense on the local wall clock.
+
+In fact, if [5] holds at this point, we do have the standard-time spelling,
+but that takes a bit of proof.  We first prove a stronger result.  What's the
+difference between the LHS and RHS of [5]?  Let
+
+    diff = x.n - (z.n - z.o)                    [6]
+
+Now
+    z.n =                       by [4]
+    (y + y.s).n =               by #5
+    y.n + y.s =                 since y.n = x.n
+    x.n + y.s =                 since z and y are have the same tzinfo member,
+                                    y.s = z.s by #2
+    x.n + z.s
+
+Plugging that back into [6] gives
+
+    diff =
+    x.n - ((x.n + z.s) - z.o) =     expanding
+    x.n - x.n - z.s + z.o =         cancelling
+    - z.s + z.o =                   by #2
+    z.d
+
+So diff = z.d.
+
+If [5] is true now, diff = 0, so z.d = 0 too, and we have the standard-time
+spelling we wanted in the endcase described above.  We're done.  Contrarily,
+if z.d = 0, then we have a UTC equivalent, and are also done.
+
+If [5] is not true now, diff = z.d != 0, and z.d is the offset we need to
+add to z (in effect, z is in tz's standard time, and we need to shift the
+local clock into tz's daylight time).
+
+Let
+
+    z' = z + z.d = z + diff                     [7]
+
+and we can again ask whether
+
+    z'.n - z'.o = x.n                           [8]
+
+If so, we're done.  If not, the tzinfo class is insane, according to the
+assumptions we've made.  This also requires a bit of proof.  As before, let's
+compute the difference between the LHS and RHS of [8] (and skipping some of
+the justifications for the kinds of substitutions we've done several times
+already):
+
+    diff' = x.n - (z'.n - z'.o) =           replacing z'.n via [7]
+            x.n  - (z.n + diff - z'.o) =    replacing diff via [6]
+            x.n - (z.n + x.n - (z.n - z.o) - z'.o) =
+            x.n - z.n - x.n + z.n - z.o + z'.o =    cancel x.n
+            - z.n + z.n - z.o + z'.o =              cancel z.n
+            - z.o + z'.o =                      #1 twice
+            -z.s - z.d + z'.s + z'.d =          z and z' have same tzinfo
+            z'.d - z.d
+
+So z' is UTC-equivalent to x iff z'.d = z.d at this point.  If they are equal,
+we've found the UTC-equivalent so are done.  In fact, we stop with [7] and
+return z', not bothering to compute z'.d.
+
+How could z.d and z'd differ?  z' = z + z.d [7], so merely moving z' by
+a dst() offset, and starting *from* a time already in DST (we know z.d != 0),
+would have to change the result dst() returns:  we start in DST, and moving
+a little further into it takes us out of DST.
+
+There isn't a sane case where this can happen.  The closest it gets is at
+the end of DST, where there's an hour in UTC with no spelling in a hybrid
+tzinfo class.  In US Eastern, that's 5:MM UTC = 0:MM EST = 1:MM EDT.  During
+that hour, on an Eastern clock 1:MM is taken as being in standard time (6:MM
+UTC) because the docs insist on that, but 0:MM is taken as being in daylight
+time (4:MM UTC).  There is no local time mapping to 5:MM UTC.  The local
+clock jumps from 1:59 back to 1:00 again, and repeats the 1:MM hour in
+standard time.  Since that's what the local clock *does*, we want to map both
+UTC hours 5:MM and 6:MM to 1:MM Eastern.  The result is ambiguous
+in local time, but so it goes -- it's the way the local clock works.
+
+When x = 5:MM UTC is the input to this algorithm, x.o=0, y.o=-5 and y.d=0,
+so z=0:MM.  z.d=60 (minutes) then, so [5] doesn't hold and we keep going.
+z' = z + z.d = 1:MM then, and z'.d=0, and z'.d - z.d = -60 != 0 so [8]
+(correctly) concludes that z' is not UTC-equivalent to x.
+
+Because we know z.d said z was in daylight time (else [5] would have held and
+we would have stopped then), and we know z.d != z'.d (else [8] would have held
+and we we have stopped then), and there are only 2 possible values dst() can
+return in Eastern, it follows that z'.d must be 0 (which it is in the example,
+but the reasoning doesn't depend on the example -- it depends on there being
+two possible dst() outcomes, one zero and the other non-zero).  Therefore
+z' must be in standard time, and is the spelling we want in this case.
+
+Note again that z' is not UTC-equivalent as far as the hybrid tzinfo class is
+concerned (because it takes z' as being in standard time rather than the
+daylight time we intend here), but returning it gives the real-life "local
+clock repeats an hour" behavior when mapping the "unspellable" UTC hour into
+tz.
+
+When the input is 6:MM, z=1:MM and z.d=0, and we stop at once, again with
+the 1:MM standard time spelling we want.
+
+So how can this break?  One of the assumptions must be violated.  Two
+possibilities:
+
+1) [2] effectively says that y.s is invariant across all y belong to a given
+   time zone.  This isn't true if, for political reasons or continental drift,
+   a region decides to change its base offset from UTC.
+
+2) There may be versions of "double daylight" time where the tail end of
+   the analysis gives up a step too early.  I haven't thought about that
+   enough to say.
+
+In any case, it's clear that the default fromutc() is strong enough to handle
+"almost all" time zones:  so long as the standard offset is invariant, it
+doesn't matter if daylight time transition points change from year to year, or
+if daylight time is skipped in some years; it doesn't matter how large or
+small dst() may get within its bounds; and it doesn't even matter if some
+perverse time zone returns a negative dst()).  So a breaking case must be
+pretty bizarre, and a tzinfo subclass can override fromutc() if it is.
+"""
+try:
+    from _datetime import *
+except ImportError:
+    pass
+else:
+    # Clean up unused names
+    del (_DAYNAMES, _DAYS_BEFORE_MONTH, _DAYS_IN_MONTH,
+         _DI100Y, _DI400Y, _DI4Y, _MAXORDINAL, _MONTHNAMES,
+         _build_struct_time, _call_tzinfo_method, _check_date_fields,
+         _check_time_fields, _check_tzinfo_arg, _check_tzname,
+         _check_utc_offset, _cmp, _cmperror, _date_class, _days_before_month,
+         _days_before_year, _days_in_month, _format_time, _is_leap,
+         _isoweek1monday, _math, _ord2ymd, _time, _time_class, _tzinfo_class,
+         _wrap_strftime, _ymd2ord)