I'm accustomed to running a git comparison that will allow comparison with local git revs like:

git diff HEAD HEAD~110 -- some/file/path/file.ext

Is it possible to use the date instead? And if so, how? I would like to be able insert in place of the "110" in the above example, a date such as "4 Dec 2012".

解决方案git diff HEAD 'HEAD@{3 weeks ago}' -- some/file/path/file.ext

This is not, strictly speaking, the revision made three weeks ago. Instead, it's the position HEAD was at three weeks prior to the present. But it's probably close enough for your purposes - it will be very accurate if the current branch's HEAD moved forward steadily, as most tend to do. You can improve the accuracy by using a branch name instead of HEAD.

Instead of an offset-from-the-present, you can also use a date/time, like HEAD@{1979-02-26 18:30:00}. See git help rev-parse.