The mtimes aren't being munged. mtimes are filesystem metadata that reflect when the file was changed; trying to use them as version control information (or application level metadata) is wrong. For example, mtimes are used by programs that cache file data, like file indexing programs; backdating mtimes will break everything that uses mtimes for their intended purpose.
Yep, and a lot of backup software will use them (along with file size, and other stat() fields) to determine if a file has changed, so backdating them can actually lead to silently stale backups
Sometimes search indexing and build tools get it wrong, so if you know what you're doing, then tools like this allow you to provide an override.
Just browsing an old photo collection without making any changes can cause a 15 year old file to show up as a "new file", even though it's contents have not changed. This is especially true with media files that the os might take it upon itself to regenerate metadata for.
Or you may wish to store an accurate snapshot of the timestamps of cached or intermediate build artifacts.
Both Finder and explorer.exe will mung mtimes from casual browsing, usually due to metadata updates.
It is a common enough problem that there are utilities to bind mtimes to files.
IMO mtime the de-facto file timetsamp metadata, since it is most widely supported. The other file timestamp metadata I found were not as useful or portable.
And people use git for storing more than just source code.
I personally find it very useful to be able to clone my podcast index and have accurate timestamps not just from the commit, but from the file itself.
Timestamps can be important for a collections of files, but they are fragile and often an afterthought.
