List of Jewish months 

Jewish months are observed on a lunar calendar.

Jewish Month	Approximate Secular Date	This Month’s Special Dates
Nissan Abib in the bible	March–April	Passover
Iyar	April–May	Lag B’Omer
Sivan	May–June	Shavuot
Tammuz	June–July
Menachem Av	July–August	Tisha B’Av
Elul	August–September
Tishrei	September–October	The High Holidays (Rosh Hashanah and Yom Kippur), Sukkot, Shmini Atzeret, and Simchat Torah
Marcheshvan	October–November
Kislev	November–December	Chanukah
Tevet	December–January	Conclusion of Chanukah
Shevat	January–February	Tu B’Shvat
Adar	February–March	Purim

Source: Chabad.org

How Jewish months evolved

In the 4th century CE, the sage Hillel II foresaw the disbandment of the Sanhedrin, and believed that Jews would no longer be able to follow a Sanhedrin-based calendar. So Hillel and his rabbinical court established the perpetual calendar which is followed today.

According to this calendar, every month of the year, except for three, has a set number of days:

• Nissan—30
• Iyar—29
• Sivan—30
• Tamuz—29
• Menachem Av—30
• Elul—29
• Tishrei—30
• Mar Cheshvan—29 or 30
• Kislev—29 or 30
• Tevet—29
• Shevat—30
• Adar—29 (in leap years, Adar I has 30 days)

The calendar in the Book of Enoch

Chapter 82 of The Book of Enoch documents the human  calendar that the author observes:

• 364 days per year.
• Each day of the year is marked by "heads over thousands" or specific stars.
• 12 months per year.
• 30 days per month.
• 4 quarters in each year.
• Each quarter consists of 90 days + 1 intercalated day.
• The  beginning of each quarter is marked by an intercalated/intercalary day.
• These intercalated days divide the four portions of the year.
• The intercalated day is marked by the appearance of specific stars.
•  The intercalated days (equinoxes and solstices) are not included in the  calendar.
• New years begin in Spring, on the day after the Spring Equinox.
• The signs of the New Year and Summer are given in detail.

NB: Lunar and solar cycles

• The lunar and solar calendars describe the cycles of these luminaries and NOT the calendar that humans are to follow.
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