использовать Datetime's timedelta .
Пример:
>>> from dateutil.parser import parse
>>> datetime = '2019-07-01 11:00:00+00'
>>> d = parse(datetime)
>>> d
datetime.datetime(2019, 7, 1, 11, 0, tzinfo=tzutc())
>>> from datetime import timedelta
>>> d = d + timedelta(minutes=25)
>>> d
datetime.datetime(2019, 7, 1, 11, 25, tzinfo=tzutc())