Use UTC dates

[Lonami]

python-telegram-bot/telegram/utils/helpers.py

Lines 78 to 90 in 4397903

	def from_timestamp(unixtime):
	"""
	Args:
	unixtime (int):
	Returns:
	datetime.datetime:
	"""
	if not unixtime:
	return None
	return datetime.fromtimestamp(unixtime)

Should probably be using tz=timezone.utc. Python's datetime isn't the best, and fromtimestamp by default sets no tz information, which uses the local time, which in turn is generally a bad idea.

[Eldinnie]

@Lonami I guess we all agree it should be UTC, but it is a breaking change. Maybe we can get it in before official v12 release?

[PaulSonOfLars]

I agree, since there's a breaking change spree for v12, might as well add this in