half past four o'clock (also acceptable) four-thirty in the afternoon (also acceptable) 4:30 p.m. (informal) 4:30 p.m. in the afternoon (informal)

Is 4/30 considered afternoon or evening?

12:01 p.m. – 5:59 p.m. is afternoon. 6:00 p.m.- 11:59 p.m. is evening.

Is five-thirty or evening in the afternoon?

A: "Half after five o'clock" is the traditional wording, but if you feel that sounds too formal, you can certainly use "five-thirty in the afternoon" or "in the evening." Also, "afternoon" is fine, for the reasons you've given, even though five-thirty is technically evening.