Film Canon ---------- In the film adaptation, Hogwarts has an enormous [Clock Tower][1] in the centre of the main courtyard. It seems to chime on the hour and half-hour throughout the day [![enter image description here][2]][2] Book canon ---------- **They have clocks on the walls** > The following week dragged by. Wednesday night found Hermione and > Harry sitting alone in the common room, long after everyone else had > gone to bed. **The clock on the wall had just chimed midnight when the > portrait hole burst open.** Ron appeared out of nowhere as he pulled off > Harry’s Invisibility Cloak. He had been down at Hagrid’s hut, helping > him feed Norbert, who was now eating dead rats by the crate.<sub><sup>HP:Philosopher's Stone - Chapter 14</sub></sup> **and upright clocks** > ‘No, no, no,’ said Hermione. ‘No, we’re not. Why don’t you go to bed, > Neville?’ Harry looked at the grandfather clock by the door. They > couldn’t afford to waste any more time, Snape might even now be > playing Fluffy to sleep. <sub><sup>HP:Philosopher's Stone - Chapter 16</sub></sup> Presumably these clocks are *literally* clockwork, which wouldn't be affected by magic restrictions on electronics. **Our three heroes wear wrist-watches** - **Ron:** > ***‘Nearly six,’ said Ron, checking his watch** and then staring down the > drive which led to the front gates. ‘How d’you reckon they’re coming? > The train?’* - **Harry:** > ***Harry crept past them to the portrait hole and waited for a minute or > so, keeping an eye on his watch.** Then Hermione opened the Fat Lady for > him from outside as they had planned. He slipped past her with a > whispered ‘Thanks!’ and set off through the castle.* - **Hermione:** > ***Hermione was tugging at his sleeve, staring at her watch**. ‘We’ve got > exactly ten minutes to get back down to the hospital wing without > anybody seeing us – before Dumbledore locks the door’* ---------- For the record, there may be [magical watches][3] (Dumbledore seems to have one) but the rest of the characters seem to rely on mundane clocks and wristwatches, all of which seem to work fine inside Hogwarts: > *Professor McGonagall pulled out a lace handkerchief and dabbed at her > eyes beneath her spectacles. Dumbledore gave a great sniff as he took > a golden watch from his pocket and examined it. It was a very odd > watch. It had twelve hands but no numbers; instead, little planets > were moving around the edge. It must have made sense to Dumbledore, > though, because he put it back in his pocket and said, ‘Hagrid’s late. > I suppose it was he who told you I’d be here, by the way?’* [1]: http://harrypotter.wikia.com/wiki/Clock_Tower [2]: https://i.sstatic.net/vMibs.jpg [3]: http://harrypotter.wikia.com/wiki/Albus_Dumbledore's_pocket_watch