Shalom All:

Here is the break-down of a Jewish day as I got it from a Messianic Ministry.
According to them this is different from the Roman division and it seems it is the sunset/sunrise factor.

Watch of the Night:  (Jewish day begins at Sunset)
Sunset to 9 PM - 1st
9 PM to 12 midnight - 2nd
Midnight to 3 AM - 3rd
3 AM to Sunrise - 4th

Hours of the Day:
Sunrise to 9 AM - 1st
9 AM to 12 noon - 2nd
Noon to 3 PM - 3rd
3 PM to Sunset - 4th

The sunset-sunrise time must not vary much in Israel so they can follow it.  Those of us who live above/below their equator position see a great fluxuation in sunrise/sunset time!!

 Dianne