What is the grammatically correct way to write p.m. and a.m.?

If I am sending out an email inviting people to a conference call, do I say 11a.m., or 11am, or 11AM , etc?
Also, do I capitalize the words Eastern or Pacific time?

I think it would be correct to write:
“11 a.m. Pacific time”
is that right? anyone know how to find a citation for this type of grammar question? I tried looking at mla.org but couldn’t figure out how to search for this type of thing.