Time of Day – No. For example, in AP style, always write “a.m.” and “p.m.” Those are lowercase. You also write “afternoon,” “morning,” and “evening” as lowercase. Even when paired with a day of the week (Ex: Monday night), it's still lowercase.

Should Good evening be capitalized?

The opening greeting in a letter also known as a salutation is always delivered capitalized, and since good evening is so commonly used as that first greeting it is commonly delivered with both words capitalized.

Is afternoon in good afternoon capitalized?

Typically, “good morning” is capitalized only when it's used as a salutation at the beginning of a letter or email. The same rule applies to “good afternoon.” Don't capitalize it unless it's a salutation in a letter or email.