How to wake up Arduino with an rtc?
If you use the DS3232RTC library then you can setup an alarm which is like an alarm. I have put a good tutorial on how to do that below.
https://thekurks.net/blog/2018/2/5/wakeup-rtc-datalogger
There is also other threads on arduino.cc you should check out. They might have additional work-arounds.
https://forum.arduino.cc/index.php?topic=333654.0
https://forum.arduino.cc/index.php?topic=99588.0