%Y should return an error when parsing a non-4 digit year

[matiu2]

Currently parsing a year like 19 with %Y will return 0019.

It should return an error because the year doesn't have 4 digits.

Users should use %y (lowercase) for 2 digit years and %Y for 4 digit years.

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Use case:

I hit this bug while porting a program from python, where it tries to parse the date in different formats in order (to clean up dirty data).

The input is: 30-09-19 (and we expect the format %Y-%m-%d to fail, and later on the format: %d-%m-%y to catch it) (It should September 30th 2019).

In the rust version I'll have to either check that the year is not too far in the future, or re-arrange the order that we check the different formats in.

[quodlibetor]

Hm, yeah I agree that this is incorrect. The correct logic seems like it should be that %Y: require zero-padding for years in the range 0 - 999, allow arbitrarily large years in either direction.

I would be uncomfortable breaking this in a 0.4.x release but we could do something like %#Y or to force strict checking.