Timekeeping during dungeon exploration is a crucial component for any game session and it's up to the DM to note this detail. Time keeping is important in knowing when to roll for wandering monsters, how long a spell may last as well as the use of torches, lanterns and other PC resources.
This gaming aid will help the DM keep track of rounds, turns and monsters encountered during a game session. It's based on my Campaign Journal gaming aid but has been simplified just for time keeping during dungeon exploration.
Time keeping is just a mechanic of the game and doesn't have to slog down game play. If PCs explore a room for example, a turn is checked off and descriptions are given. A DM doesn't have to drag time out.
Time keeping notes:
I usually just check off the time whether it be rounds or turns. If I'm keeping track of Torches or Spells, I use a notation T6 for a torch lasting 6 turns, S3 for a Spell lasting 3 turns, P12 for a Potion lasting 12 turns etc. You can use whatever system you like for the above mentioned or any other item you like such as Effects of poison or duration of spells effects.
In my campaign each round lasts 10 seconds; so 6 rounds is equal to 1 minute and 60 rounds is equal to a single turn (if combats take that long)
I usually mark a completion of a turn after a melee, the extra time being taken up resting, binding wounds, etc.
According to the 1st ed DMG (pg 38), A party should be required to rest 1 turn every 6. I don't always use this rule but I think it is a good one. It doesn't have to slow the game down either. Just checking off an additional turn is all that is needed.
Searching a 30X30 space takes 1 turn
Searching for a secret door along a 30 foot section of wall takes 1 turn.
If players discuss a course of action their PC should take, depending on how long the conversation takes place, I may check a turn off.
Torches traditionally last 6 turns or 1 hour. This can sometimes be amended to make things more interesting by letting them burn for 1d4+4 turns (from BFRPG). To keep it simple I usually go with just the 6 turn torch.