0.23.5 changes the default kerbin day to 6 hours so the manuever nodes are reporting 4x what mechjeb is reporting and it's making me nuts trying to set up my orbital period to rendezvous with asteroids! Is there any plans to give us a swtich to choose 24 or 6 hours days so we can get in sync with the game settings???

Better would be to simply respect the clock setting throughout mechjeb the setting name is (GameSettings.KERBIN_TIME).

I recently had to do this work in kOS and it is not too bad. I ended up having to build my own DateTime object that anyone is welcome to use.
https://github.com/KSP-KOS/KOS/blob/master/Suffixed/Timespan.cs

it has a bit of kOS in it simply because it is interrogatable by kerboscript

Slightly ahead of you @ctbram; I implemented this a couple of days ago. Try dev build 258 (but not 259 or 260, those were built from the master branch instead of the dev branch because of a mistake I made):

http://jenkins.mumech.com/job/MechJeb2/258/

This version should respect the in-game setting for 6h vs 24h days.