[Python] タイムゾーン変換

import datetime

class JST(datetime.tzinfo):
    def utcoffset(self, dt):
        return datetime.timedelta(hours=9)
    def dst(self, dt):
        return datetime.timedelta(0)
    def tzname(self, dt):
        return "JDT"

class EDT(datetime.tzinfo):
    def utcoffset(self, dt):
        return datetime.timedelta(hours=-4)
    def dst(self, dt):
        return datetime.timedelta(0)
    def tzname(self, dt):
        return "EDT"

edt = datetime.datetime(2007,07,25,12,00,tzinfo=EDT())
jst = edt.astimezone(JST())
print jst.isoformat(" ")