Fix date parsing bug, now timezones on all objects

[brondsem]

def cast_date was using datetime.timezone.utc which was wrong because datetime was the object not the module. This error was caught but it meant the dp.parse path was never running.

Now that its fixed, many timestamps get parsed with a timezone attribute they didn't have before. I went ahead and made all parsing (no matter via dp.parse or datetime_parse) to have a timezone for consistency.

[richardpenman]

Thanks for all this work!