dedstikyfingerz
Normally the ATZ hours are coincident with the published ATS hours. However, I know of at least one airfield, Warton, where the ATZ is notified H24, despite ATC not being there all the time. Also caution should be exercised as some airfields have out of hours activities like ambulance flights which require a licensed airfield. In these cases the ATZ will be activated at short notice via NOTAM. It is always worth calling on the appropriate frequency out of hours just to make sure.