Reply To: Tal Umotor Reminder

The climate chages through the seasons determined by the sun whereas Jewish holdays are determined through the moon. Pesach is spring and Succos fall time causes a Jewish leap year 7 times in 19 years in order that lunar year having normally 354 days and the solar year 365 1/4 days even itself out. The pnemonic is guchadzut, 3, 6, 8, 11, 14, 17, 19 year in 19 years becomes a Jewish leap year. A calendar is available in the Tur after siman 428 which enumerates each of the 19 years determined by Cheshvan and Kislev if they are deficient, both 29 days, full, both 30 days or even one 29 days and the other 30 days. The rest of the months cycle between 29 and 30 days. 6×29 + 6×30 = 174 + 180 = 354 days. The variation of the two months above causes the movement of Rosh Hashanah as Adu lo Rosh, the Rosh Hashanah cannot fall on Wednesday or Friday. Rosh Hashanah cannot be on a Sunday in order Hashanah Rabba should not fall on a shabbos eliminating the knocking off the hashanas.