Post # 1
My wedding is at four o’ clock in the … evening or afternoon? I can’t seem to find which is the proper wording for the invites. The ceremony and reception are in a barn and will be more casual, if that makes any difference.
Post # 3
Four o’clock (by the way, no space between the apostrophe and clock) in the afternoon. There’s debate over whether evening begins at five or six, but four is definitely in the afternoon.
You can omit it if you want to. No one is going to show up at four o’clock in the morning. We did ours as “at half past two o’clock,” “at six o’clock,” etc., with nothing after that.