I understand why we have a leap year; to keep the sun and moon cycles in sync, so that Pessach is always in the spring.

That's all technical, as a result of the moon orbiting too slowly - or the sun too fast.

On a philosophical / theological level, why did Hashem create the world in such a way that a leap year is needed?

What does Hashem expect to achieve (or rather expect us to achieve/accomplish) with this extra month?

Surely there's some aspect of Avodat Hashem that depends (or can be improved) by understanding the point of the The Leap Year concept.

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    Why did Hashem create the world requiring some months to have 29 days and some months to have 30 days? Commented Mar 12, 2014 at 14:08
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    @C.BenYosef - kind of a related question, on a smaller scale, but more frequent. Commented Mar 12, 2014 at 15:21
  • yagdil torah...
    – ray
    Commented Jul 20, 2015 at 17:23
  • Interesting Q. But I think there is a given premise as to why the Judaic year is based on the moon rather than the sun. One reason I heard is that just as the moon waxes and wanes, so too do the Jewish people - they lose strength and regain it. Also, the moon reflects the light from the sun like Jews reflect the light of Torah from G-d. Based on this premise, and the need to coordinate our calendar with solar b/c of Pesach, thus the need for leap years.
    – DanF
    Commented Aug 3, 2015 at 21:53
  • @DanF - you don't think it's possible to create a model that the moon cycles are an exact fraction of the sun's cycle? IOW the lunar cycle could have been 30.4.. days long instead of 29.5... days long. Commented Aug 4, 2015 at 7:05

4 Answers 4


To solar cycle represents continuity and consistency. The lunar cycle represents rise and fall, והחיות רצוא ושוב.

The two cycles don't inherently mesh, and it takes the actions of people (as represented by Beis Din which sets the leap year) to combine the two.

See here for a similar expression of this idea.

In terms of lessons in Avodas Hashem, there are many. But one obvious one is that in Torah you have the idea of Chiddush (innovation) - כל מה שתלמיד ותיק עתיד לחדש נתנה למשה מסיני - Whatever a zealous student will innovate was given to Moshe at Sinai (Yerushalmi Peah Chapter 2). Questions, answers and uncertainty on the one hand, but with the solid basis of Torah MiSinai on the other.

It takes zealous learning (Beis Din) to create a chiddush in harmony with Torah Misinai, and not מגלה פנים בתורה שלא כהלכה - propounding ideas as Torah which contradict Halacha.

  • Thanks, @Yishai, but I am still left with my questions - why is the leap year needed, and what does Hashem expect to achieve (or rather expect us to achieve/accomplish) with this extra month? Commented Mar 13, 2014 at 9:56
  • @DannySchoemann, Um, the answer certainly attempts to address those questions. Perhaps you can elaborate on how you feel they remain unanswered?
    – Yishai
    Commented Mar 13, 2014 at 13:28
  • you are doing a great job explaining the lunar cycle and its lessons. But you are not explaining what "the extra Adar" is supposed to teach us. (Assumption: It can't just be an "accident" of the disjoint between the solar and lunar calendars.) Commented Mar 23, 2014 at 10:56
  • @DannySchoemann, you mean an extra month generally, or a second Adar specifically?
    – Yishai
    Commented Mar 24, 2014 at 21:00
  • Reb @Yishai, as a first stab, I'd like to understand why there's an extra month every so often (7/19 years) - what does Hashem want/expect us to do with this extra month? As a bonus we can discuss why it's Adar in particular. Commented Mar 25, 2014 at 9:47

A different angle on the question: at the funeral for Rabbi Emanuel Gettinger (who was a mathematics and astronomy enthusiast), it was suggested that God values our engaging the world. This way, we would have to study astronomy to determine how to modify the calendar.

(Recall that the Gemara praises the role of an honest human judge as "partnering with God.")


It does have the effect of making Adar longer with its increased happiness. (This is an incomplete answer, but I can not just add a comment)


As explained in this article the ideal Jewish year is actually 13 months (representing a dominance of the Jewish lunar calendar over the non-Jewish solar one) and it will resume this cycle in the days of Moshiach. The leap month is added to provide access to the future redemption even in our times.

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    For the record: (Anonymous) article claims it's an idea from the מהרש"א in Sanhedrin 12a Commented Jul 21, 2015 at 11:48

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