Is 5pm on invitation the afternoon or evening??

Evening

You can avoid this altogether since one doesn't need to specify that a wedding is at 5pm instead of am, but really it's the afternoon

Evening isn't until 6

Evening technically starts at 6 PM. 5 PM is still afternoon.

@Sheri OP never said anything about serving a meal or not. Off subject.

Evening. You're having an afternoon wedding and an evening reception.

I like evening

5:01pm is evening

@VegasWed: 5PM is in the afternoon. You are correct.

While it's bright daylight at 5 pm in May, I'd lean toward evening. The reception will certainly go into the nighttime hours, rather than be a daytime, garden party affair.

Why not word with "Join us for late afternoon cocktails, dinner and dancing"? This will keep everybody happy.