Stewarton Bible School

Part 2 ... File 5 of 10

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Question 5

Why do some years in the Sacred Calendar have 13 months?


In the Sacred Calendar normal years have 12 months and leap years have 13 months. The extra month is periodically added to keep Yahweh's Festivals in step with the agricultural seasons in Israel (Deut.16:6). Agricultural produce (flocks, grain, fruit, wine, oil etc.) are shadows and types of the spiritual realities and fruit Yahweh is producing in the lives of His people. In order to keep these spiritual lessons in mind the Most High arranged for His Festivals to coincide with the agricultural seasons in Israel.

Lev.23:4 These are the feasts of the LORD, even holy convocations, which ye shall proclaim in their seasons.
Exo.34:22 And thou shalt observe the feast of weeks, of the firstfruits of wheat harvest, and the feast of ingathering at the year's end.
But what have these facts to do with adding a 13th month? To explain further. The moon orbits the earth in just over 29.5 days. A twelve lunar-month year totals about 354 days. This is about 11.25 days short of a 365.25 day tropical (sun) year. If a 13th month were not added periodically, Abib would begin about 11 days earlier each year. The month would retreat to winter, then autumn, then summer and Yahweh's festivals would not occur 'in their seasons' as required by the law. For example, the Feast of First Fruits (Pentecost) could then occur in the middle of winter, when there would be no fruit in the field. In the 12 lunar-month Islamic calendar the festivals occur about 11/12 days earlier each year. This can be seen in the chart below:

Civil YearIslamic New YearRamadan
198814 August18 April
19894 August7 April
199024 July28 March
199113 July17 March
19922 July5 March

In the sacred calendar the festivals must coincide with the agricultural seasons: Passover in spring, First Fruits in the summer and Tabernacles (ingathering of the main harvest) in the autumn. To maintain this order, a thirteenth month must be added periodically to make up for that annual 11.25 day loss.

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Author: David B Loughran
Stewarton Bible School, Stewarton, Scotland
Updated: August 1998