How well do characters know the time?

Question

The Keen Mind feat (PHB, p. 167) says:

You have a mind that can track time, direction, and detail with uncanny precision. You gain the following benefits.

• Increase your Intelligence score by 1, to a maximum of 20.
• You always know which way is north.
• You always know the number of hours left before the next sunrise or sunset.
• You can accurately recall anything you have seen or heard within the past month.

This seems to imply that, by default, a character does not necessarily know "the number of hours left before the next sunrise or sunset" or remember what they may have read in books regarding reading time by the stars, planets, or sun position.

Is there any temporal information that characters necessarily know by RAW, or is it all up to the DM's judgment with respect to the situation (e.g. a Knowledge check for astronomy, or access to a town square where a calendar might be posted)? For example, if PC's have been imprisoned in a windowless cell, they might not know the exact clock time or even the correct time of day, but they intuitively know the exact number of calendar days that have passed since they were thrown in.

Answer 1

Characters can tell time about as well as any normal person...

^{(and about as well as it's interesting for them to know)}

Barring a a session of video games or something else very interesting, you and I know about what time it is.

Sometimes you lose track of time, but it doesn't come up a lot. Granted, I don't know off hand what the exact time the sun rises or sets, but I can make do.

Then, what is the benefit of this ability?

DM judgment. The only real time this would come up is if the DM wants it to come up. The DM can create some sort of complication or constraint where proper time keeping is important.

Examples include (but are not limited to)

• Being in a dungeon at sunset and having something to do at sunrise.
• Something that's sensitive to the moon or sun (i.e. - werewolves or vampires).
• Being on another plane where time moves differently.
• some sort of "ticking clock" puzzle where the party has to know or do something at an exact time.

This is also an opportunity for the DM to empower players. If one of the players at my table takes Keen Mind, I'm going to be looking for ways to make exact time telling important, or knowing where North is.

Answer 2

Keen Mind reveals spatial disturbances that might not otherwise be immediately apparent.

Whereas most characters of course know or can figure out what directions are what sorts of north on the Material Plane, and generally know both how many hours are between sunrise and set and vice versa as well as which of those hours they are currently in and in addition know fairly well what they've been doing for the last month, a character with Keen Mind knows these things even across planes and time portals, and even when planar transitions and temporal alterations might otherwise be subtle.

Particularly in dungeons with subtly turning and/or sloping corridors, teleportation effects to identical rooms, or sections seamlessly transitioning onto other planes, Keen Mind gives a character instant access to information they would otherwise need to be using powerful divination magics to find out.

Answer 3

I'd say that characters know the following about time: night, noon, beforenoon, and afternoon. They also know the sequence of events, such that if something happened in the beforenoon, but it is not yet noon, then they know that they are in-between those "sequence points" and closer to noon that it was earlier.