diff options
Diffstat (limited to 'Doc/includes/tzinfo-examples.py')
-rw-r--r-- | Doc/includes/tzinfo-examples.py | 46 |
1 files changed, 38 insertions, 8 deletions
diff --git a/Doc/includes/tzinfo-examples.py b/Doc/includes/tzinfo-examples.py index 5a2b8ad..2de95d4 100644 --- a/Doc/includes/tzinfo-examples.py +++ b/Doc/includes/tzinfo-examples.py @@ -87,11 +87,31 @@ def first_sunday_on_or_after(dt): dt += timedelta(days_to_go) return dt -# In the US, DST starts at 2am (standard time) on the first Sunday in April. -DSTSTART = datetime(1, 4, 1, 2) -# and ends at 2am (DST time; 1am standard time) on the last Sunday of Oct. -# which is the first Sunday on or after Oct 25. -DSTEND = datetime(1, 10, 25, 1) + +# US DST Rules +# +# This is a simplified (i.e., wrong for a few cases) set of rules for US +# DST start and end times. For a complete and up-to-date set of DST rules +# and timezone definitions, visit the Olson Database (or try pytz): +# http://www.twinsun.com/tz/tz-link.htm +# http://sourceforge.net/projects/pytz/ (might not be up-to-date) +# +# In the US, since 2007, DST starts at 2am (standard time) on the second +# Sunday in March, which is the first Sunday on or after Mar 8. +DSTSTART_2007 = datetime(1, 3, 8, 2) +# and ends at 2am (DST time; 1am standard time) on the first Sunday of Nov. +DSTEND_2007 = datetime(1, 11, 1, 1) +# From 1987 to 2006, DST used to start at 2am (standard time) on the first +# Sunday in April and to end at 2am (DST time; 1am standard time) on the last +# Sunday of October, which is the first Sunday on or after Oct 25. +DSTSTART_1987_2006 = datetime(1, 4, 1, 2) +DSTEND_1987_2006 = datetime(1, 10, 25, 1) +# From 1967 to 1986, DST used to start at 2am (standard time) on the last +# Sunday in April (the one on or after April 24) and to end at 2am (DST time; +# 1am standard time) on the last Sunday of October, which is the first Sunday +# on or after Oct 25. +DSTSTART_1967_1986 = datetime(1, 4, 24, 2) +DSTEND_1967_1986 = DSTEND_1987_2006 class USTimeZone(tzinfo): @@ -122,9 +142,19 @@ class USTimeZone(tzinfo): return ZERO assert dt.tzinfo is self - # Find first Sunday in April & the last in October. - start = first_sunday_on_or_after(DSTSTART.replace(year=dt.year)) - end = first_sunday_on_or_after(DSTEND.replace(year=dt.year)) + # Find start and end times for US DST. For years before 1967, return + # ZERO for no DST. + if 2006 < dt.year: + dststart, dstend = DSTSTART_2007, DSTEND_2007 + elif 1986 < dt.year < 2007: + dststart, dstend = DSTSTART_1987_2006, DSTEND_1987_2006 + elif 1966 < dt.year < 1987: + dststart, dstend = DSTSTART_1967_1986, DSTEND_1967_1986 + else: + return ZERO + + start = first_sunday_on_or_after(dststart.replace(year=dt.year)) + end = first_sunday_on_or_after(dstend.replace(year=dt.year)) # Can't compare naive to aware objects, so strip the timezone from # dt first. |