This project is a combination of various factors. I wanted a way of converting the date to the Jewish (solar-lunar) date, display it in Hebrew characters, calculate various times that are relevant in Jewish Law, sunrise, sunset, nightfall, latest time for reciting Krias Shema, day of the omer etc. I also wanted an alarm clock that rings a set time before the latest Krias Shema time, with a snooze button, which would be deactivated on shabbos and yom tov. On shabbos and yom tov, the alarm rings for a full minute, 20 minutes and 3 minutes before the deadline; on weekdays it rings continuously from 20 minutes before until 2 minutes before, with a snooze button (the reset button).
The device runs on a Nano, but since I intend to add GPS functionality (to determine location; relevant for sunrise and sunset - currently location is hard-coded, and to keep the time) and an IR remote control (to manually adjust the location and time), I will either have to use a Mega (as not enough memory on the Nano or Uno) or make the program smaller and with less memory.
Due to the 2kb size of the Nano's bootloader, you will need to replace this with the Uno's bootloader, which is a quarter of the size.
Additionally, remove the diode from the RTC to disable the dangerous charging circuit.
The Hebrew Date is calculated using Gauss's Passover formula, found here: https://en.wikibooks.org/wiki/Mathematics_of_the_Jewish_Calendar/Gauss%27_Formula_for_the_Date_of_Pesach