How to set Alarms on the DS3231 easily so the Nano doesn't have to go to sleep with delay statements?
Here it is:

https://github.com/sleemanj/DS3231_Simple

Example:  https://github.com/sleemanj/DS3231_Simple/blob/master/examples/z2_Alarms/Alarm/Alarm.ino

This is what I was looking for.  

My system needs to be able to respond to radio remote commands while asleep, and the long delay() statements were preventing that.  

These alarms solve the problem.