Time

In situations where keeping track of the passage of time is important, the DM determines the time a task requires. The DM might use a different time scale depending on the context of the situation at hand. In a dungeon environment, the adventurers' movement happens on a scale of minutes. It takes them about a minute to creep down a long hallway, another minute to check for traps on the door at the end of the hall, and a good ten minutes to search the chamber beyond for anything interesting or valuable.

In a city or wilderness, a scale of hours is often more appropriate. Adventurers eager to reach the lonely tower at the heart of the forest hurry across those fifteen miles in just under four hours' time.

For long journeys, a scale of days works best. Following the road from Baldur's Gate to Waterdeep, the adventurers spend four uneventful days before a goblin ambush interrupts their journey.

In combat and other fast-paced situations, the game relies on rounds, a 6-second span of time.
Swimming across a rushing river, sneaking down a dungeon corridor, scaling a treacherous mountain slope--all sorts of movement play a key role in fantasy gaming adventures.

The DM can summarize the adventurers' movement without calculating exact distances or travel times: "You travel through the forest and find the dungeon entrance late in the evening of the third day." Even in a dungeon, particularly a large dungeon or a cave network, the DM can summarize movement between encounters: "After killing the guardian at the entrance to the ancient dwarven stronghold, you consult your map, which leads you through miles of echoing corridors to a chasm bridged by a narrow stone arch."

Sometimes it's important, though, to know how long it takes to get from one spot to another, whether the answer is in days, hours, or minutes. The rules for determining travel time depend on two factors: the speed and travel pace of the creatures moving and the terrain they're moving over.