What is ante-meridian?

Answer 1

Time before noon.

Before the use of standard time, (Greenwich Mean Time, time zones, etc.) most communities used solar time. Every town had its own standard of time. Noon was when the sun reached its highest point in the sky on any given day. Solar noon happens at the moment of the sun's transit of the meridian; the geographical north- south imaginary line directly overhead that the sun and other celestial bodies cross. Before the sun crosses the meridian it is morning. After the sun crosses the meridian it is afternoon (post meridian). In modern times we still use the a.m. and p.m. designations, even though they are not technically correct.