This patch adds:
Feel free to give me any feedback you could have. (:
Sorry I didn't respond earlier, I'm in half-holidays.
The reason I did not merge your patch is because depending on the time for a build is not always a good idea. Some build and deployment systems (such as NixOS and Nixops) aim at ensuring perfect build reproducibility: with the same build inputs, you're supposed to get the same outputs (i.e. binaries have the exact same bytes).
A feature like this one in a build system would break these guarantees. It might break updates, either by forcing unneeded updates, or by failing to detect that some piece of information (date and time) needed for the build has changed.
Maybe we can just keep the development/release version information, in such a case?