See datetime.tzinfo.fromutc

def fromutc(self, dt):
        '''See datetime.tzinfo.fromutc'''
        dt = dt.replace(tzinfo=None)
        idx = max(0, bisect_right(self._utc_transition_times, dt) - 1)
        inf = self._transition_info[idx]
        return (dt + inf[0]).replace(tzinfo=self._tzinfos[inf])