from calendar import monthrange
 
 
def datetime():
    day = 0
    month = 0
    year = 0
    day, month, year = map(int, input("Enter date: ").split(sep='.'))
 
    while year not in range(0000, 10000) or len(str(year)) < 4:
        year = int(input("Year must be at range of 0000 to 9999 "))
    while month not in range(1, 13):
        month = int(input("Month must be at range of 1 to 12 "))
    while day not in range(1, monthrange(year, month)[1]+1):
        day = int(input("Day must be at range of 1 to %s " % monthrange(year, month)[1]))
 
    print('%s.%s.%s' % (day, month, year))
 
datetime()
 

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MTIuMTIuMTk5OQ==

12.12.1999