There are a number of different timepieces within the Harry Potter series:
The Time-Turner is a small silver hourglass worn on a chain around the neck. It’s a very powerful and dangerous magical item which literally turns back time for the user, one hour per inversion of the glass.
A wizarding pocket watch may have an unusual number of hands, or have symbols other than numbers along the edge of the face, or both.
There is a clock with only one hand and no numbers marked "Time to make tea, time to feed the chickens, You're late" - in the kitchen of the Burrow (CS3)
A Grandfather clock with nine golden hands located in the Weasley living room, this fine clock is completely useless if you need to know the time. Instead it has a hand for each of the Weasley family members. These hands point to inscriptions around the face which indicate where that person is at the moment. Some of the words on this clock are "home," "school," "work," "traveling," "lost," "hospital," "prison," and "mortal peril" (GF10).
Dark Magic grandfather clock
located in number twelve, Grimmauld Place, this rather nasty clock would shoot heavy bolts at passers-by. (OP6)
From the Web
How do people at Hogwarts usually tell the time? from scifi.stackexchange