duration of days in the northern hemisphere?

Answer 1

24 hours although it often seem like less.

Answer 2

The duration of daylight varies with the latitude of the observer and with the seasons. At the poles daylight varies from 24 hours (during local summer) to 0 hours (local winter). As you move closer to the equator daylight hours diminish until (at the vernal and autumnal equinoxes) they are each 12 hours (more or less..the equinoxes occur only for an instant, so it is unlikely you would observe exactly equal day and night). Also, you must consider atmospheric refraction, which causes the sun to rise early and set early with regard to the astronomical times (refraction by the atmosphere bends the light of the sun to cause this).

Answer 3

It depends on where. Slightly North to the Equator is already the Northern Hemisphere and the North Pole is there too. In my country (Hungary) it's 10 hours now.