outdated.py

def main():
    months = ["January",    "February",    "March",    "April",    "May",    "June",    "July",    "August",    "September",    "October",    "November",    "December"]

    while True:
        try:
            date = input('Date: ').strip()
            parts = date.split('/')
            mm = int(parts[0])
            dd = int(parts[1])
            yyyy = int(parts[2])
        except:
            try:
                parts = date.split(', ')
                yyyy = int(parts[1])
                mon_dd = parts[0].split(' ')
                dd = int(mon_dd[1])
                mm = months.index(mon_dd[0])+1
            except:
                continue
        if (1 <= dd < 31) and (1 <= mm <= 12) and yyyy >= 0:
            break

    print(f'{yyyy:04}-{mm:02}-{dd:02}')

main()