I had a question recently about how it is that the Scriptures refers to Passover being in the month of Aviv but it is also said to be in the month of Nisan. I thought others may be interested in the answer, so I am posting it here.
The Hebrew or Jewish calendar is split between the pre-exilic and the post-exilic calendars ; i.e. before and after the Babylonian exile.
I – Prior to the Babylonian exile:
There are only 4 ‘months’ from this pre-exilic calendar that are named in the Old Testament;
Aviv; the first ‘month’, (mentioned in Ex 13:4, Ex 34:18 in association with Passover). Aviv comes from the Hebrew word איבה pronounced ‘eebeha’ literally “greenness.”
The other three months are:
These are believed to be Canaanite or Phoenician names and are often explained by rabbinic sources to refer to the 4 seasons.
References: Jewish Encyclopedia (see calendar) & Hachlili, R., Ancient Synagogues – Archeology & Art: New Discoveries and Current Research (2013)
However, Aviv is named as the 1st month, Ziv as the 2nd month, Ethanim as the 7th month and Bul as the 8th month.
These are 4 months in the pre-exilic calendar; i.e. before the Babylonian exile.
The problem with this calendar is that it was based on observation alone to determine when the months were. One had to see the new moon to know that a new month was starting. If the sky is clear, that isn’t a problem but what if the new moon wasn’t observable?
This led to the practice of celebrating the ‘new moon’ / beginning of the new month over two days, as seems to be indicated in 1 Samuel 20:27
Reference: International Standard Bible Encyclopedia
Where do these pre-exilic months appear in Scripture?
Aviv – Ex.12:2, Deut 16
Ziv – 1 Kings 6:1,37
Ethanim – 1 Kings 8:2
Bul – 1 Kings 6:38
II – After the Babylonian exile (597 BC)
After the Babylonian exile (597 BC), Jews started using the Babylonian month names, which are still used. We know from passages like 1 Chron 27: 1-15 that there are 12 months and each new month (literally the beginning of the month) is called Rosh Chodesh and is celebrated (see Num 10:10 or Num 28:11).
Months in the Bible are numbered; so there is the first month, the second month, etc.
These are the month names used since the Babylonian exile and where these month names occur in Scripture:
- Nisan – Neh 2:1 & Esther 3:7
- Sivan – Esther 8:9
- Tammuz – Ex 8:4 (Tammuz is a Phoenician deity after whom the month was named)
- Elul – Neh 6:15
- Kislev Neh 1:1, Zech 7:1
- Tevet – Esther 2:16
- Shevat – Zech 1:7
- Adar – Ezra 6:15 (and mentioned several times in Esther)
It is important to note that numbers and letters in Hebrew are one and the same; so the number 1 is “א” pronounced ‘aleph’ (like the letter ‘A’) and the number 2 is “ב” pronounced ‘bet’ (like “B”), etc.
So the alphabet (yes, aleph-bet!) are also the numbers 1, 2, 3…etc
After the Babylonian exile (597 BC), Jews started using the Babylonian month names, which are still used.
Reference: DeVaux, JH, Ancient Israel: Its life and Institutions (1961)
These are the month names used since the Babylonian exile:
As the Jewish calendar is a lunar calendar, every 3 years or so, there is a “leap month” to make up the difference between the lunar calendar (~354 days) and the solar calendar, like the Gregorian (of 365 days). Those years are called ‘leap years’ but instead of having only an extra day (like in the Gregorian calendar), Jewish leap years have a whole extra month.
These extra months were added by the priests to make sure that the feasts were celebrated at the proper times (Jewish Encyclopedia, see calendar). If the sun had not reached the vernal equinox on the 16th of Nisan, the extra month was added. So there would be two months of Adar (Adar and the ‘second Adar’), followed by the first month of Nisan. This of course was not exact and around the 4th century, a mathematical basis for adjusting for the difference between the lunar and solar calendar was adopted (Jewish Encyclopedia, see calendar). It is as follows:
Most years, there is the usual 12th month called Adar and then 7 times every 19 years there is this “leap month” called Adar ‘aleph’; which is to make up the difference between the lunar calendar and the solar calendar. The Jewish leap year occurs at regular intervals; specifically on the
year in this cycle.
So on a “leap year” there are 13 months, as follows;
- Adar ‘aleph’
So when is Passover?
We know that Passover falls on the 14th day of the first month i.e. the 14th of Nisan on the post-exilic calendar.