What time of the day is considered as afternoon and evening?

Taking into consideration that we all know that morning and afternoon are both separated at exactly 12:00 PM and that the whole day has 24 hours (almost 24 but the difference is already accumulated every 4 years on february). If you take 24 and divide it by 3, which is Morning, Afternoon and Evening, you would get 8 hours. So each time of day lasts exactly 8 hours. Now looking at where Afternoon start and going forth from there we would get the following:

12:00 PM - 8:00 PM --> AFTERNOON

8:00 PM - 4:00 AM --> EVENING

4:00AM - 12:00PM --> MORNING

to be more precise it would be

12:00 PM - 7:59:59 PM --> AFTERNOON

8:00 PM - 3:59:59 AM --> EVENING

4:00AM - 11:59:59 AM --> MORNING

So basically you could say Good morning at 4:05 AM, Good Evening at 8:05 PM and Good Afternoon at 7:59 PM.