Time marches ever forward, and the world moves on without you. Time is poorly modeled in most d20 systems. Although there is supposed to be a drawback to spending excessive amounts of time on tasks, that’s very seldom the case in actual play, allowing time to slip away without meaning. This system brings time back into play in a meaningful way without adding too many fiddly bits.
The Time Pool
The core of this system is the Time Pool. Whenever the players spend a meaningful amount of time on a task, a die is added to the pool. These dice are an abstraction for time and represent somewhere between 5 and 15 minutes of in game time each.
When there are 6 dice in the Time Pool, the dice are rolled, clearing the pool and advancing the game clock by 1 hour. If any of the dice roll a 1, then the situation just got worse. Maybe the players face a random encounter, maybe the torch sputters out, or maybe the bad guy has had enough time to pull off whatever dastardly deed he had planned.
Time is not your friend.
Adding Time Dice
When the players commit to an action that takes more than just a couple of minutes, time passes, adding a die to the pool. Whether this is thoroughly searching a room, deciphering eldritch runes, or simply reading a book, the passage of time doesn’t go unnoticed.
Time Dice are typically d8s. In more dangerous situations, the Time Die added might be a d6 or even a d4. In more peaceful places, the Time Die might be a d10 or d12.
Time spent in combat never adds Time Dice to the pool.
Rolling Time Dice
Whenever a Time Die would be added to the pool, the GM may choose to roll any number of the dice already in the pool instead of adding a new die. If none of the rolled dice result in a 1, then all rolled dice are returned to the pool, and play continues. If at least one die rolls a 1, Bad Stuff™ happens. The more 1s rolled, the worse the Bad Stuff™ becomes. All dice that rolled a 1 are removed from the pool, the rest are returned, and play continues.
If there are already 6 Time Dice in the pool, then the Time Pool is considered full. If a die should be added when the Time Pool is full, then the GM [I]must[/I] roll the dice instead of adding a new die. After the dice are rolled, all dice are cleared from the pool, even if none of them rolled a 1.
Game time advances by one hour only when the Time Pool is full, rolled, and then cleared in this manner.