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This Monday, 6 Tevet, will be my 19th birthday. This year’s birthday has something very interesting. It’s going to be the first time since my birth that my birthday on the Jewish calendar will coincide with my birthday on the Gregorian calendar.
As we know, the Jewish holidays (as well as the Jewish birthdays) do not always occur on the same date in the Gregorian calendar. For instance, Chanukah this year started on December 10 while last year, it started on December 22.
Why is there such a difference?
There are various ways to count the years. One way is to follow the yearly cycle of the sun. This cycle is about 365 days, which we divide in 12 months.
Another way is to follow the monthly cycle of the moon, with each new moon signaling the beginning of a new month. This monthly lunar cycle is 29 ½ days. It follows that 12 lunar months make a year of 354 days.
Whoever knows arithmetic will see that there is a difference of 11 days between the solar and the lunar year.
The Gregorian calendar follows the first way, the solar cycle. The Jewish calendar combines both ways. In other words, it is based on the lunar month but also on the solar year. How is this possible and why is it needed?
The Torah commands us to count the years according to the moon, and this is why the Jewish people count the months according to the New Moon. But the Torah commands us as well to celebrate Passover during the spring season.
There is a problem here. If we count the year only according to the moon, we “lose” 11 days every year in comparison with the solar cycle. After a few years, we will have “lost” so many days that Pesach will fall in the winter.
This is why our Sages have devised the Jewish calendar, where we add an extra lunar month (Adar I) every couple of years. In this way, after 19 years, the gap between the solar and the lunar years is resolved. In other words, after 19 years, the same number of days will have passed in the Jewish calendar as well as in the solar cycle (the Gregorian calendar).
Thus, the Jewish Holidays occur on various days in the Gregorian calendar, but Pesach is always celebrated in the spring. And every 19 years, the Jewish date coincides with the Gregorian date.
The next time my Jewish birthday (6 Tevet) will coincide with my Gregorian birthday (December 21), I will be 38 years old!
Shabbat Shalom,
Arie from the Yeshiva
