afternoon or evening

Put whichever you feel sounds better...either way, no one is going to show up in the morning. Sometimes this etiquette stuff makes my head spin :o This would be one of those times : )

Neither. Your guests can figure that you aren't getting married at 5 in the morning.

Evening

I would put evening

I've found documentation both ways -- e.g., http://blog.invitationbox.com/2009/03/25/invitation-etiquette-your-faqs-answered/

We put afternoon for our 5pm wedding.

We should have just put PM! Too late for us.

We just said "at half past 5" for our 5:30 ceremony. Fingers crossed none of our guests are clueless enough to show up at 5:30 AM !

Evening

I say evening.

Orrrr to be super sure , you can just say 17:00 without evening or afternoon