Kirtan is to be done in Raags.

Timings of Raags

TIME OF THE DAY OR NIGHTRAAGS 
6 am to 9 am
http://saadavirsa.com/raags-for-6-am-to-9-am/
9 am to 12 noon
12 noon to 3 pm
3 pm to 6 pm
6 pm to 9 pm
9 pm to 12 midnight
12 midnight to 3 am
3 am to 6 am