A measurement of time found on a map

Question: I'm a measurement of time.
But you'll find me on a map, not a clock.

What am I?

Question: What fish only swims at night?

Question: What do you call a mad elephant?

Question: What kind of mouse does not eat, drink or even walk?

Question: What has a bed that you can't sleep in?

Question: Where do all the letters sleep?