Names of Hebrew Months
Hebrew Calendar Rules
Holy Days Dates

Postponements are part of the process of calculating and declaring the date of the Feast of Trumpets (Tishri 1, the first day of the Hebrew sacred year), which in turn is used to set the year's dates for observing God's annual Holy Days.

After calculating the Molad of Tishri, the following postponement rules are used to declare Tishri 1:

• Rule One:
  When the Molad of Tishri or advancement occurs on a Sunday, Wednesday, or Friday, the declaration of Tishri 1 is advanced one day to a Monday, Thursday or Saturday (Sabbath) respectively.

• Rule Two:
  When the Molad of Tishri occurs at or after noon (18 hours 0 parts), the declaration of Tishri 1 is advanced to the next day.

• Rule Three:
  When the Molad of Tishri of a common year falls on a Tuesday, at or after 9 hours and 204 parts, the declaration of Tishri 1 is advanced to Wednesday. The application of Rule One advances the declaration one more day to Thursday.

• Rule Four:
  When the Molad of Tishri of a common year immediately following an intercalary year occurs on a Monday, at or after 15 hours and 589 parts, the declaration of Tishri 1 is advanced to Tuesday.

Common year:
A 12-month year in the Hebrew Calendar. A deficient common year contains 353 days, a regular common year contains 354 days, and a perfect common year contains 355 days.

Hour:
A measurement of time in the Hebrew Calendar equating to 1080 parts or 3600 seconds. The use of hours has the advantage of eliminating fractions. Hours are calculated from 6 PM; thus 6 hours equates to 12 Midnight, 12 hours equates to 6 AM, and 18 hours equates to 12 Noon.

Intercalary year:
A 13-month year in the Hebrew Calendar. A 30-day month called Adar I is added in years 3, 6, 8, 11, 14, 17, and 19 of each 19-year cycle. The result is a year with 383, 384 or 385 days. Also referred to as a leap year.

Molad:
The calculation of the average conjunction of the moon with the earth and the sun; it is based on the mean or average length of the lunar month, which is 29.53059 days. The Molad is not the astronomical conjunction.

Part:
A measurement of time in the Hebrew Calendar equating to 3 1/3 seconds. There are 18 parts to a minute and 1080 parts to an hour.

Postponement:
A one or two-day adjustment to the calculation of the Molad of Tishri. These adjustments enable the process of calculating the Molad to consistently achieve the greatest degree of accuracy in relationship to the cycle of the moon.