In Eretz Yisrael we start saying V'Sain Tal U'Matar on the 7th of Cheshvan. If someone from Eretz Yisrael will be in America on the 7th of Cheshvan and will be flying back to Eretz Yisrael a few days ...
I'm trying to pin down an algorithm for calculating when to start saying ותן טל ומטר in diaspora. (In Israel it begins 7 Cheshvan.) I've gotten that we need to know how many centuries passed since ...