That's the problem, quite a lot of functions like leds values calculations, moonlights etc relies on RTC so if you commented that code out then unpredictable behaviour will happen.
I'd leave the code as it is, it should work without RTC clock connected, there will be just weird numbers instead of time and date.
That was after I first started the sketch. When I first ran it (without editing the code) it would flash the main screen then reset everything. I was then messing around with it, commented out the RTC stuff, then i got past the main screen to a menu and that wouldnt let me do anything. Thats understandable though, and just an observation.