@dtelder @0xabad1dea

This is a programming error. The library behaves exactly as documented:
https://docs.python.org/3/library/datetime.html#technical-detail

"For the datetime.strptime() class method, the default value is 1900-01-01T00:00:00.000: any components not specified in the format string will be pulled from the default value."

If you want your software to handle leap years correctly, you have to give it a chance to know which year we are talking about 😉