0 GˆÎÍ „yðºïÌÁÏ?÷G"""Concrete date/time and related types. See http://www.iana.org/time-zones/repository/tz-link.html for time zone and DST data sources. """ __all__ = ("date", "datetime", "time", "timedelta", "timezone", "tzinfo", "MINYEAR", "MAXYEAR") import time as _time import math as _math import sys 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. # -1 is a placeholder for indexing purposes. _DAYS_IN_MONTH = [-1, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] _DAYS_BEFORE_MONTH = [-1] # -1 is a placeholder for indexing purposes. 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 preceding 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