Re: How long does the new moon last?

The simple answer to your question is that it depends on how hard you 
look! The record for seeing the new Moon is only about 12 hours after it 
was new (that is, completely dark). However, it only becomes obvious after 
a day or two, when the cresent becomes bright enough to easily be seen by 
the naked eye.

The trouble is that at or near new Moon, the Moon is very close to the Sun 
in the sky. So to spot it you need to wait until after sunset, and then 
look very close to the horizon; normally things like trees and houses will 
get in the way, so to see the earliest Moon possible get high up, or 
better still somewhere with an ocean view.