School opdracht niet kwijt raken please

Zuyd Logica Dag van de week.py

DAYS_IN_MONTH = (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31)
MONTH_NUMBER  = [0, 3, 3, 6, 1, 4, 6, 2, 5, 0, 3, 5]
YEAR_NUMBER = [0,1,2,3,5,6,0,1,3,4,5,6,1,2,3,4,6,0,1,2,4,5,6,0,2,3,4,5]
CENTURY_NUMBER = [6, 4, 2, 0]
DAYS = ["zondag", "maandag", "dinsdag", "woensdag", "donderdag", "vrijdag", "zaterdag"]

def problem():
  print("Deze datum is ongeldig.")

def yearnumber(year):
  y = year
  while y > 27:
    y = y - 28
  return YEAR_NUMBER[y]

def centurynumber(century):
  c = century
  while c > 3:
    c = c - 4
    # 15 > 3, 16 > 0, 17 > 1, 18 > 2
  return CENTURY_NUMBER[c]

def date(): 
  date_str = input("Voer een datum in (dd-mm-YYYY): ")
  parts = date_str.split('-')

  if len(parts) != 3: 
    problem()
  else:
    for i in range(len(parts)):
      parts[i] = parts[i].strip()
      if len(parts[i]) == 0 or not parts[i].isdigit():
        problem()
    return int(parts[0]), int(parts[1]), int(parts[2])


def valid_date(day, month, year):  
  if month < 1 or month > 12 or day < 1 or year < 0:
    return False
  
  days_in_month = DAYS_IN_MONTH[month - 1]
  if month != 2:
    return day <= days_in_month
  if year % 400 == 0 or year % 4 == 0 and year % 100 != 0:
    days_in_month += 1
  return day <= days_in_month

def main():

  given_date = date()
  if valid_date(given_date[0], given_date[1], given_date[2]):
    # Datum is geldig
    year = (given_date[2] % 100) % 7
    century = int((given_date[2] - year) / 100) + 1
    
    print(DAYS[2 + (given_date[0] + MONTH_NUMBER[(given_date[1] - 1)] + yearnumber(year)  + centurynumber(century)) % 7])

  else:
    # Datum is ongeldig!
    problem()



main()