How does GNU make keep track of file changes?

Question

So when you run make without changing any of the dependencies it says target upto date. I was curious how it keeps track of changes to the files, does it have some kind of revision control system under the hood. If so, where are these files stored?

Answer 1

No, it just compares the last-modified dates of the files.

If the target is newer than all of its dependencies, it's up to date. Otherwise the relevant dependencies are re-built.