from datetime import datetime, tzinfo, timedelta
import time

class timezone(tzinfo):
    def __init__(self, offset, name=None, dst=None):
        self.offset = offset
        self.name = name
        self.dst_ = dst
    
    def utcoffset(self, dt):
        return self.offset
    
    def dst(self, dt):
        return self.dst_

    def tzname(self, dt):
        if self.name is None:
            offset = self.offset
            sign = '+'
            if offset < timedelta(0):
                offset = -offset
                sign = '-'
            return 'UTC%c%02d%02d' % (sign, offset.hours,
                                      offset.minutes)
        return self.name


EPOCH = datetime(1970, 1, 1)
STDOFFSET = timedelta(seconds=-time.timezone)
DSTOFFSET = timedelta(seconds = -time.altzone)
DSTDIFF = DSTOFFSET - STDOFFSET
STDDIFF = timedelta(0)
def localtime(utctime=None):
    if utctime is None:
        tm = time.localtime()
    else:
        seconds = (utctime - EPOCH).total_seconds()
        tm = time.localtime(seconds)
    
    tz = (timezone(DSTOFFSET, time.tzname[1], DSTDIFF)
          if tm.tm_isdst else
          timezone(STDOFFSET, time.tzname[0], STDDIFF))
    return datetime(*tm[:6], tzinfo=tz)

if __name__ == '__main__':
    for t in [localtime(), localtime(datetime.utcnow()),
              localtime(datetime.utcfromtimestamp(0))]:
        print(t.tzname(), t, t.timetuple().tm_isdst)