I thought I would say (may have already been said) but because of the longer hours of sun I have found my syrian not waking up until around 9pm when he used to be up around 6pm on the dot (he's been slowly waking up later and later). So I would also assume that when autumn/winter comes around again the hammy may start gettting up a bit earlier.
I have to wake up one of my dwarfs since he really doesn't leave his nest for anything or than food or water and he seems happy enough, although I do always reward with a treat when he goes back into his cage.
likewise as some have mentioned, they are often awake in the early hours of the morning (sometimes I can hear a wheel going off from one of my robo's cages around 5/6am).