Daytime: Sunrise to sunset.
Nighttime: Sunset to sunrise.

Morning: The full 12 hours of 'AM'.
Afternooon: Midday to roughly 5-6pm.
Evening: Roughly 5-6pm through to midnight.

In New Zealand it was easier as you could say that evening was after the sun had set through to midnight, and afternoon was midday through to sunset. However over here it's a little trickier as sunset ranges between something like 3pm and close to midnight depending on the time of the year. xD

I have no idea why some people complicate matters by insisting that night and evening/morning can't both occur at once. If it can be both day and afternoon at the same time, why can't it be both night and evening?