Start of month of Adar I (on leap years) on the Hebrew calendar. Adar I (אַדָר א׳) is the 12th month of the Hebrew year, occursonly on leap years, has 30 days, and corresponds to February or March on the Gregorian calendar. רֹאשׁ חוֹדֶשׁ, transliterated RoshChodesh or Rosh Hodesh, is a minor holiday that occurs at the beginning of every month in the Hebrew calendar. It is marked by the birth of a new moon
Torah: Numbers 28:1-15
https://hebcal.com/h/rosh-chodesh-adar-i-2027?uc=ical-marietta
