Kiddush Hachodesh – part 2

Today we are going to learn about the seasons, to understand when spring starts. The Beis Din would decide to make a leap year sometimes (13 months) to make sure Pesach is at the beginning of the spring.

There are two ways the Rambam shows us how to figure out the seasons, because there are two different opinions on how long a SOLAR (sun) year is!
1) 365 days and 1/4 day (6 hours)
2) 365 days, 5 hours, 997 parts, and 48 moments (a part has 76 moments)

According to the first opinion (365.25 days):
Like we learned yesterday, the LUNAR (moon) year is 1 hour and 485 parts longer than the solar year.

Every season starts 91 days, 7.5 hours after the other season. So if you know when one season starts, you can just add 91 days, 7.5 hours to figure out when the NEXT season will start.

We can divide the sky up into 12 parts, each of them with a group of stars. These groups of stars have names. When the sun goes into a certain part of the sky, that’s when that season starts (because it means the sun is closer or further away from us, making it colder or warmer).

SPRING – (Nisan) – when the sun goes into Aries
SUMMER – (Tamuz) – when the sun goes into Cancer
FALL – (Tishrei) – when the sun goes into Libra
WINTER – (Teves) – when the sun goes into Capricorn

In the year Hashem made the world, spring started 7 days, 9 hours, and 642 parts before the Nisan molad.

So here’s how to figure out when a season starts:
1) Figure out how many Machzors (groups of 19 years) passed since Hashem made the world
2) Add 1 hour and 485 parts for each Machzor
3) Take away 7 days, 9 hours, and 642 parts
4) Add this number to the time of the Nissan molad for the first year in THIS Machzor
5) Now you can add 91 days, 7.5 hours to find out when each season starts.