RE
“We add 14 from 2100”
Yes my #5 is wrong I tried to repost without it but both went up
“So let’s use the rule that it is Dec 4th. except before a leap year when it is Dec 5th.”
Yep that is the rule.
AaQ I don’t understand .
The calculation doesn’t work because it isn’t the way to calculate.
It’s 60 days from tekufas Tishrei using Tekufas Shmuel. Not 61 days from the autumnal equinox. Yes they often overlap but shpukdnt expect them to be the same .
Tekufas Shmuel is known to be flawed There is a more accurate tekufa of Rav Ada, bit we font use it for this because too complicated (Chazon Ish says this)