Depends on the airplane, I would imagine. As to 'manually' setting, that also would depend on the source of the master clock. Some older and less sophisticated (electronically) aircraft still go by the captain's chrono while others have digital aspirations that put the master in an equipment rack down below with access sometimes granted via the FMC/MCDU. In my experience, UTC sources include GPS and dispatch uplink syncs.
I seem to be no help on this so far Chappy!
Any chance you have an aircraft type in mind?