Venue: YU Torah MiTzion Beit Midrash Zichron Dov YU Torah MiTzion Beit Midrash Zichron Dov

Gemara:

Rosh Hashana 

Halacha:

Jewish Calendar 

Collections: Rabbi Torczyner Minchas Chinuch

References: Rosh Hashana: 21b ,  Minchas Chinuch: 4:2 ,  Rambam: Hilchos Kiddush haChodesh 3:15-19  

Description

The Minchas Chinuch uses the Rambam's concept of retroactive kiddush hachodesh - the idea that beis din could receive witnesses late in the month, and be forced to change the date of the previous Rosh Chodesh - to explain why witnesses break Shabbos to reach beis din, and to explain the view of R' Elazar b"R' Tzaddok on why beis din does not declare "Mekudash" for a 30 day month.