How specific is a clerics "time to meditate" to get their spells back

Question

in the cleric page on the SRD it says

Clerics meditate or pray for their spells. Each cleric must choose a time at which she must spend 1 hour each day in quiet contemplation or supplication to regain her daily allotment of spells.

It doesn't say how much of a buffer zone they have. For example say my meditation time is midnight but I get stuck in an encounter around that time. How long before and after that is the "safe zone". Most classes require a long rest before they can regain their class features (at least to my knowledge they do). So only needing 1 hour would be game-breaking if there wasn't a time restriction in place. On the other hand, if the time restriction is too picky you could be locked out of your spells for a prolonged period of time due to bad luck with encounters or just being in transit at the wrong time, which would be underpowered.

So that begs the question, how close do you have to be to the time you choose to meditate in order to get your daily spells.

Answer 1

You have to stop and pray at the first opportunity near that time.

If we look at the rules for preparing divine spells, we see (emphasis mine):

Time of Day: A divine spellcaster chooses and prepares spells ahead of time, but unlike a wizard, does not require a period of rest to prepare spells. Instead, the character chooses a particular time of day to pray and receive spells. The time is usually associated with some daily event. If some event prevents a character from praying at the proper time, she must do so as soon as possible. If the character does not stop to pray for spells at the first opportunity, she must wait until the next day to prepare spells.

Thus we can see that a cleric must prepare spells at their normal time. If they're prevented from doing so by something such as combat, they must then do so as soon as they get the opportunity. If they fail to do so, they are unable to prepare spells until the next day.