I don't think this form on timestamping is necessary, personally.  Seems we wouldn't get an end event if you ctrl+c to exit early etc.  If we want to benchmark the pieces of MCA workflow, lets move this helper inside mca.js..

Also, this is exposing globals ts, addTs, mca on the global object, so I would suggest wrapping in an anonymous scope (function() { ... }()).

Anyway, I think this is what the "time" command is for.