I came up with some ideas how to add 30 days. But code should add 31 days if this month has 31 days or 28 , for example, if it is Febuary. The only library that should be used is datetime. This is what i came with.
def get_next_month(date):
month = (date.month % 12) + 1
year = date.year + (date.month + 1 > 12)
datetime.datetime(year, month, 1)
But it's not completely correct(