timezone without pytz

timezone.py

from datetime import tzinfo, timedelta


class UTC(tzinfo):
    def utcoffset(self, dt):
        return timedelta(seconds=0)

    def dst(self, dt):
        return timedelta(seconds=0)

    def tzname(self, dt):
        return 'UTC'

    def __repr__(self):
        return '<UTC+00:00>'


class KST(tzinfo):
    def utcoffset(self, dt):
        return timedelta(hours=9)

    def dst(self, dt):
        return timedelta(seconds=0)

    def tzname(self, dt):
        return 'KST'

    def __repr__(self):
        return f'<{self.__class__.__name__}+09:00>'


utc = UTC()
kst = KST()