Greetings!

"Hello" can be used at any time of day.

You can say "hello" in a formal and an informal setting.

"Hi" can also be used at any time of day.

You can say "hi" in a formal and informal setting.

"Hey" can be used at any time of day.

"Hey" is an informal greeting.

"Good Morning!" 

This is a greeting but is only used until 12pm.

In an informal setting or in passing in the street most people shorten it to "morning".

"Good afternoon"

This is a greeting you can use from 12pm to 6pm.

"Good Evening"

This is a greeting used after 6pm.

In informal settings many people shorten it to "evening".

"Good Night"

This is only used as a way to say good bye in the evening.

Many people shorten it to "Night!".

"Goodbye" or "Bye"

You can say this when you are leaving.

You can say this any time of the day.