In situations where keeping track of the passage of time is important, the GM determines the time a task requires. The GM 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.