There's a good amount of code in MWTimestamp that is generally re-usable. Some methods are MW specific and probably shouldn't be in MWTimestamp to begin with...
- getHumanTimestamp - https://gerrit.wikimedia.org/r/213355
- offsetForUser (depends upon User and $wgLocalTZoffset)
- getRelativeTimestamp - unused???
- getLocalInstance (dependent upon $wgLocaltimezone)