Affected synsets

https://en-word.net/lemma/a.m. (Adjective)
https://en-word.net/lemma/A.M. (Adverb)

and similarly:

https://en-word.net/lemma/p.m. (Adjective)
https://en-word.net/lemma/P.M. (Adverb)

Proposed changes
I think these items should include alternative forms found in wiktionary.org (links below).

Also, wiktionary.org only has adverbs for these items. This is just a note, I am not an English speaker to say anything about this.

Motivation
https://en.wiktionary.org/wiki/a.m.#English
https://en.wiktionary.org/wiki/p.m.#English