In PL/SQL Block, I would like to print the 'Good Morning','Good Noon','Good Eve' based on the system time that I have given as input.  

If the time is 6 AM to 12 PM then it has to print GOOD MORNING 
else if 
it lies between 12 PM to 2 PM 
it has to print GOOD NOON 
else if it has to print GOOD EVE. So anybody can give me the Idea? 
Advance Thanks for everyone who gives me the guidance.