Patching Git to handle dates before the Unix epoch

As people use Git to create synthetic commits of code written in the past [1,2] it becomes important to handle dates before the Unix epoch (1/1/1970). I see that modern C libraries, Unix kernels, and tools can handle such dates. However Git seems to mishandle such dates in several places, such as in date.c [3,4]. I'm planning to work on a fix, but before I embark on this I have a few questions.

- Do you see any reasons that may prevent the acceptance of such a patch?
- Can you think of any non-obvious issues (e.g. backward compatibility, 
switch to the Gregorian calendar) I should be aware of?
- Should I submit changes as a bug fix on the maint branch or as a new 
feature on master?

[1] https://github.com/dspinellis/unix-history-repo (original dates) [2] https://github.com/chrislgarry/Apollo-11 (wrong dates) [3] https://github.com/git/git/blob/master/date.c#L21 [4] https://github.com/git/git/blob/master/date.c#L776

Diomidis Spinellis - https://www.spinellis.gr