Good Morning friend,
I'm no expert - but I've been taught the following;
I hope I can be of some assistance;
The polite greeting: "Good Morning!" can be used anytime from Midnight (24:00) onwards until Mid-day (12.00) .
"Good Afternoon!" can be used from Midday (12.00) till five o'clock - (17.00)
It is only at this time that one uses the greeting "Good Evening!"
This phrase can be used until Midnight (24:00) - unless you wish to depart from someone's company. Which is when one uses the phrase "Good Night!".
Best wishes -
Jackalina the Wise