max() min()

from datetime import datetime
dt=datetime(2019,12,31)
print(dt.min)
print(dt.max)

0001-01-01 00:00:00
9999-12-31 23:59:59.999999

Using a list

my_date=['2021-03-23','2019-04-15','2021-07-26','2019-12-22']
print(min(my_date)) # 2019-04-15
print(max(my_date)) # 2021-07-26