AM is ante meridian and PM is post meridian. It's referenced to the prime meridian through Greenwich UK. If the sun is to the east of the line (ie. Before noon where it is vertical) it's before (ante) the meridian. If it's after (post) noon it's after the meridian. It's all outdated but that's how time works.
AM is ante meridian and PM is post meridian. It's referenced to the prime meridian through Greenwich UK. If the sun is to the east of the line (ie. Before noon where it is vertical) it's before (ante) the meridian. If it's after (post) noon it's after the meridian. It's all outdated but that's how time works.