This only seems helpful for people who have no access to windows - it gives you an idea of how the day is progressing in such general terms, my brain without a watch could guess the time with a similar degree of accuracy by glancing out the window combined with an inherent sense of time passing.
Elaine: What time you got?
Kramer: Oh, no. I don't wear a watch.
Elaine: What do you do?
Kramer: Well, I tell time by the sun.
Elaine: How close do you get?
Kramer: Well, I can guess within an hour.
Elaine: Well, I can guess within the hour, and I don't even have to look at the sun.
Kramer: Yeah.
Elaine: Well, what about at night? What do you do then?
Kramer: Well, night's tougher but it's only a couple of hours.