This phrase is used as a standard greeting for English speakers in the morning. Further, this phrase is only used until 12 p.m. (noon). If you try to use it in the afternoon, you might get a few funny looks.
Good afternoon.
Meaning:
Good afternoon is the phrase you should use, and though the line between afternoon and evening is a little blurry, you can use this phrase until 5 p.m.
Good evening.
Meaning:
Evening generally takes place between 5 p.m. and 10 p.m., some say evening goes right until the moment you fall asleep.
Hello / Hi / Hey.
Meaning:
Don’t want to be confused about what time of day it is? You can use these phrases.
How are you? / How is it going?
Meaning:
This question normally comes after the greetings above, and it is used to ask someone how they are feeling.