Beginning of new Hebrew month of Sivan. Sivan is the 3rd month of the Hebrew year. Corresponds to May or June on the Gregorian calendar https://www.hebcal.com/holidays/rosh-chod

Festival of Weeks, commemorates the giving of the Torah at Mount Sinai https://www.hebcal.com/holidays/shavuot?utm_source=js&utm_medium=icalendar