Should AM and PM be capitalized?
AM and PM should usually not be capitalized, but different style guides have different requirements. Unless your style guide says otherwise, “a.m.” and “p.m.” should be lowercase with a period after each letter (e.g., “I’m serving dinner at 7:30 p.m.”).
When writing “a.m.” and “p.m.” in lowercase, the QuillBot Grammar Checker can help you remember where to use a period.