import time
from datetime import datetime, timezone


class MyDatetime(datetime):
    pass


dt = MyDatetime.fromtimestamp(time.time())
print(dt)  # MyDatetime(2018, 11, 30, 18, 8, 36, 418105)
print(type(dt))  # <class '__main__.MyDatetime'>

dt = MyDatetime.fromtimestamp(time.time(), tz=timezone.utc)
print(dt)  # datetime.datetime(2018, 11, 30, 17, 8, 50, 667385, tzinfo=datetime.timezone.utc)
print(type(dt))  # <class 'datetime.datetime'>