Months have different lengths, there are leap years, and time zones exist. The datetime module takes care of all of it:

from datetime import date, timedelta

moon = date(1969, 7, 20)
print(moon)
print(moon.year, moon.month, moon.day)
print(moon.strftime("%A %d %B %Y"))

week_later = moon + timedelta(days=7)
print(week_later)

gap = date(2000, 1, 1) - moon
print(gap.days, "days")

date(year, month, day) makes a date.
Adding a timedelta moves a date; subtracting two dates gives a timedelta, whose .days is the number of days between them.
.weekday() gives 0 for Monday up to 6 for Sunday.
date.today() gives today's date.