I wouldn't give you the time of day!

Because Im not quite sure what it is!

How do you define morning, afternoon and evening? Is there an afternoon equivalent for midnight to sunrise?

Personally I say:

Morning - midnight to noon
Afternoon - noon to 6pm
Evening - 6pm to midnight

and i've lately been trying to coin the word "oddening" to refer to Midnight to 6am and have morning refer solely to 6am to noon

Thus an oddening starts the day and at the end of the day it is evened.

I heard some people believe afternoon lasts until dinnertime or some such nonsense and would like to know if there are any like minded individuals here with which I shall strike from my list of respected persons.

Ever since the end of the first morning, we have been locked in an eternal state of afternoon.
Never again will noon not have passed.
Alas.

Well, for me, dinnertime usually falls around 6pm so it works either way you define it. I suppose I haven't really thought about it, but:

Morning: Typically from the time you wake up until noon
Afternoon: After 12:00pm (literally: after-noon) until dinnertime
Evening: Dinnertime until sleep
Any other time between evening and morning: Why are you asking what time it is? I'm sleeping! :p

For example, if someone said to meet up in the morning, I wouldn't think that it meant anytime from midnight to noon...I would assume it meant sometime after you woke up to before lunchtime.

Morning: About 5 or 6am - 1pm
Afternoon: 1pm - about 6pm
Evening: 6 pm - about 11pm
Night: 11pm - 5 or 6 am

I just sort of estimate when I'm at work and tell people to have a nice day/evening/whatever.

Morning : 12am- 1pm
Afternoon : 1pm - 9pm
Night : 9pm+
Void : 2am - 12am

Morning: 6 AM - 12 PM
Afternoon: 12 PM - 6 PM
Evening: 6 PM - 12 AM
Night: 12 AM - 6 AM

Sorted.

Moring: 12am-12pm
noon: 12pm
after noon: 12pm-12am
evening: white tie

6 AM to 11:59 AM : Morning
12 PM: Noon
12:01 PM to 4:49 PM: Afternoon
5 PM to 8 PM PM: Evening
8:01 PM to 11:59 PM: Night
12 AM to 5:59 AM: Why aren't I asleep?

6 AM - 10 AM - Breakfast time
10 AM - 3 PM - Lunch time
3 PM - 9 PM - Dinner time
9 PM - 12 AM - Snack time
12 AM - 6 AM - Time to put on my cape and mask and prowl the streets, looking for criminals to backhand.

Morning 7:00 AM-12:00 PM
Noon 12:00 PM-5:00 PM
Evening 5:00 PM-9:00 PM
Night 9:00 PM-3:00 AM
Early Morning 3:00 AM-7:00 AM

Fast food restaurants have taught me that mornings end at ten-thirty, along with the chance to order Egg McMuffins. The rest of the day is pretty bland and generic until Dark; it is then you light a fire and keep your back to it so as to better fend off the wolves.

I think you're confusing mornings with breakfast.

Morning = 5am-12pm
afternoon = 12:01PM (geddit, it's after NOON) - 4:30/5pm (this depends on if the sun is going down earlier and dusk is coming)
evening = very short compared to the rest o ya' 4:30/5pm - 8:30/9:00
Night = the rest.

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?

It changes with the season. For summer it's like this:

Morning: Doesn't exist
Day: 12pm to 4pm
Night: 5pm to 7am