Im not sure if this is an old problem or whatever, cant seem to turn anything up in Google or the wiki.

But for whatever reason, not sure what might cause it, i suspect Fast travelling...but my time seems to be off after awhile playing the game, literally a day changes from 0000:2400 to any random number within 24 hours, like 0630 to 1770 or whatever.

Not sure if means anything, but its quite annoying if i want to check vendors or something.

You sure your not confusing 24 hour time with the day?