app/django/utils/datetime_safe.py

   1 # Python's datetime strftime doesn't handle dates before 1900.
   2 # These classes override date and datetime to support the formatting of a date
   3 # through its full "proleptic Gregorian" date range.
   4 #
   5 # Based on code submitted to comp.lang.python by Andrew Dalke
   6 #
   7 # >>> datetime_safe.date(1850, 8, 2).strftime("%Y/%M/%d was a %A")
   8 # '1850/08/02 was a Friday'
   9
  10 from datetime import date as real_date, datetime as real_datetime
  11 import re
  12 import time
  13
  14 class date(real_date):
  15     def strftime(self, fmt):
  16         return strftime(self, fmt)
  17
  18 class datetime(real_datetime):
  19     def strftime(self, fmt):
  20         return strftime(self, fmt)
  21
  22     def combine(self, date, time):
  23         return datetime(date.year, date.month, date.day, time.hour, time.minute, time.microsecond, time.tzinfo)
  24
  25     def date(self):
  26         return date(self.year, self.month, self.day)
  27
  28 def new_date(d):
  29     "Generate a safe date from a datetime.date object."
  30     return date(d.year, d.month, d.day)
  31
  32 def new_datetime(d):
  33     """
  34     Generate a safe datetime from a datetime.date or datetime.datetime object.
  35     """
  36     kw = [d.year, d.month, d.day]
  37     if isinstance(d, real_datetime):
  38         kw.extend([d.hour, d.minute, d.second, d.microsecond, d.tzinfo])
  39     return datetime(*kw)
  40
  41 # This library does not support strftime's "%s" or "%y" format strings.
  42 # Allowed if there's an even number of "%"s because they are escaped.
  43 _illegal_formatting = re.compile(r"((^|[^%])(%%)*%[sy])")
  44
  45 def _findall(text, substr):
  46     # Also finds overlaps
  47     sites = []
  48     i = 0
  49     while 1:
  50         j = text.find(substr, i)
  51         if j == -1:
  52             break
  53         sites.append(j)
  54         i=j+1
  55     return sites
  56
  57 def strftime(dt, fmt):
  58     if dt.year >= 1900:
  59         return super(type(dt), dt).strftime(fmt)
  60     illegal_formatting = _illegal_formatting.search(fmt)
  61     if illegal_formatting:
  62         raise TypeError("strftime of dates before 1900 does not handle" + illegal_formatting.group(0))
  63
  64     year = dt.year
  65     # For every non-leap year century, advance by
  66     # 6 years to get into the 28-year repeat cycle
  67     delta = 2000 - year
  68     off = 6 * (delta // 100 + delta // 400)
  69     year = year + off
  70
  71     # Move to around the year 2000
  72     year = year + ((2000 - year) // 28) * 28
  73     timetuple = dt.timetuple()
  74     s1 = time.strftime(fmt, (year,) + timetuple[1:])
  75     sites1 = _findall(s1, str(year))
  76
  77     s2 = time.strftime(fmt, (year+28,) + timetuple[1:])
  78     sites2 = _findall(s2, str(year+28))
  79
  80     sites = []
  81     for site in sites1:
  82         if site in sites2:
  83             sites.append(site)
  84
  85     s = s1
  86     syear = "%4d" % (dt.year,)
  87     for site in sites:
  88         s = s[:site] + syear + s[site+4:]
  89     return s