```
import datetime

def main():
    date_string = input('Enter a date in mm/dd/yy format: ')
    date_list = date_string.split('/')
    month = int(date_list[0])
    day = int(date_list[1])
    year = int(date_list[2])
    while month < 1 or month > 12:
        print('Month entered is out of range')
        date_string = input('Re-enter a date in mm/dd/yy format: ')
        date_list = date_string.split('/')
        month = int(date_list[0])
        day = int(date_list[1])
        year = int(date_list[2])
    while day < 1 or day > 31:
        print('Day entered is out of range')
        date_string = input('Re-enter a date in mm/dd/yy format: ')
        date_list = date_string.split('/')
        month = int(date_list[0])
        day = int(date_list[1])
        year = int(date_list[2])
    while year != 13:
        print('Year does not represent 2013')
        date_string = input('Re-enter a date in mm/dd/yy format: ')
        date_list = date_string.split('/')
        month = int(date_list[0])
        day = int(date_list[1])
        year = int(date_list[2])
    print(month, day, year)
main()

```

When I run the program and enter months and days that are invalid, it progresses down until the year validation and will keep posting that prompt even if the input is invalid for one of the other inputs.