As @flashko may have been hinting, powering 300 LEDs will be necessary.
It may be useful and save your eyes a bit of wear and tear and also mechanically weildier (easy to wield) to begin your experiments with but a small number of LEDs.
And it will be quicker if you deal for the first bit of development doing things a bit faster… very frustrating to wait around 8 hours then miss what you were waiting for, see something wrong go to bed rinse and repeat.
You could even do the LEDs coming on and change color over a period of time w/o using the RTC at all… then when the sequencing looks plausible, add the RTC to make the sequence happen precisely, maybe use seconds or minutes until it’s nearing perfect to switch to hours.
a7