Procedure that triggers upon it becoming nighttime

So, I have a procedure that I want to activate when it becomes night time.  Specifically, it is supposed to say something in chat on New Moons and Full Moons.  But I can't figure out a trigger to use other than "on world tick update", which causes the message to be spammed ever tick.  Is there any other way I can have this procedure get naturally triggered with no input from the player? (image attached)