I'm going to take advantage of this thread to talk about something else I've been wanting to which is related: 24 hour timers.
If you want players to be able to do something only once per day, don't set a 24 hour lockout. In practice, that means that if I do the thing at 8pm, then the next day I end up doing it at 8:15, cause I have other things going on. Later, it'll be at 9pm, eventually at 10pm. You get the idea. It makes play sessions inflexible, and forces players to skip days to reset their timer.
Set a 20 hour lockout instead. If I do the thing at 8pm most days, but today I can't log in until 9pm? No worries, it'll be ready to go at 5pm tomorrow, so I can play any time during my usual block. Humans need to sleep, so even if you can abuse this to do it twice in a calendar day, once in a while, it's still effectively "once per day" for most people, without the stress of perfectly scheduling your play sessions, and with less difficulty syncing up with friends if it's that sort of activity.
Daily rewards ruin games, and daily reward quests are essentially the same thing, but there are other places and reasons to use this sort of system, and 20 hours is almost always better for lockout timers than 24.