How do we know that Jesus was crucified at 9:00 a.m.? I have heard many times that Jesus was crucified at 9:00 a.m. and remained on the cross till 3 p.m.. How do we know that? The Scriptures say something like the third hour:


  Matthew 15:25: And it was the third hour, and they
  crucified him.


But how do we know that the third hour was exactly 9:00 a.m.?

Do we draw information on that point exclusively from Scriptures?

Is it something like a known fact from Hebrew tradition?

Or, perhaps, something else ?
We do not know that the third hour was exactly 9:00 AM - that is an estimation for the purpose of providing an understandable translation.

The Jewish day started at dawn and ended at dusk.  There were 12 hours, which were each 1/12th of the stretch between dawn and dusk. (More info.)

For simplicity, if we consider dawn to be roughly 6:00 AM, that would make the 3rd hour about 9:00 AM.