To switch between time zones, you need datetime objects that are timezone-aware.
from datetime import datetime
from dateutil import tz
utc = tz.tzutc()
local = tz.tzlocal()
utc_now = datetime.utcnow()
utc_now # Not timezone-aware.
utc_now = utc_now.replace(tzinfo=utc)
utc_now # Timezone-aware.
local_now = utc_now.astimezone(local)
local_now # Converted to local time.