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Genesis 1:14 says that all Appointed Times (מועדים) are determined by the Sun and the Moon Phases. For example, all Holy Meetings (מקרא קדש) in the 1st or 7th months fall on moon phases.

However, Leviticus 23:27 says that Yom Kippur is on the 10th which does not fall on any moon phase.

So which verse is correct? Genesis 1:14 or Leviticus 23:27?

marked as duplicate by sabbahillel, Gershon Gold, DonielF, mbloch, Shimon bM Nov 1 '17 at 4:54

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  • 1
    "the 10th which does not fall on any moon phase" I don't understand this. It does fall on a moon phase. The 2/3 full phase. – Double AA Oct 31 '17 at 19:39
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    Where do you see that the holidays must fall on moon phases? Maybe all the verses mean is that the months will be decided based on the lunar calendar - thus, Yom Kippur is the tenth of a lunar month, rather than a solar one. – DonielF Nov 1 '17 at 3:19
  • If you like an answer, consider marking it accepted. – mevaqesh Nov 13 '17 at 15:59

You are mistaken as to the meaning of the pasuk. The months are determined by the moon. That is each month starts with the beginning of the month at the declaration of the new moon by the Sanhedrin (or by the fixed calendar based on the moon nowadays). Thus the Torah stating that Yom Kippur is the tenth day of the seventh month shows that it starts based on the relationship of the moon (which declares the start of Tishrei - the seventh month).


Rav Saadya Gaon translates ul'moadim in 1:14 as 'times', rather than festivals. (Tafsir there).

Rav Qafih explains (notes there) that rav saadya gaon's point is that holidays are not solely dependant on heavenly bodies. Rather, in his opinion holidays follow days of the month which are primarily defined by calendrical calculations.

Targum Onkelos similarly renders it 'times'. This is also the understanding of Ibn Ezra (there).

Furthermore, even if it meant that the constellations determine holidays, it could mean that the festivals follow the day of the month, but the months themselves could be based on the moon. Thus the moon is still the determinant. That is, the holiday would be some number of days after the new moon.


The Hebrew word for month is חדש which literally means 'newness' (i.e. being new). That is, a Hebrew "month" is simply a calculation of days in terms of the new moon (an occurrence that happens to take place 12 times a year).

Yom Kippur occurring on the tenth of the month is thus by definition tied to the calculation of the moon.

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