Shavua Me'ûber: The Epagomenal Week

A time outside of time

In YHWH Original Calendar, the first day of the year always falls on the first Wednesday after the spring equinox. However, due to the difference between the solar cycle and the 364-day calendrical cycle, an adjustment, known as intercalation, is necessary occasionally to synchronize with the tropical year.

This intercalation is referred to as the 'epagomenal week' or in Hebrew, 'שבוע מעובר' (Shavua Me'ûber), which literally translates to 'pregnant week' or 'leap week'. This term is used in the Hebrew calendar context to denote an additional week added to certain years. 

The YHWH Calendar's system is based on the number 7, including its intercalation method, which involves adding a block of 7 days, equivalent to a week. Approximately every 5-6 years, when the vernal equinox aligns with the first Wednesday (which is the fourth day after the Sabbath) of the year, an additional block of days is automatically inserted into the 364-day count, ensuring synchronization with the solar cycle alongside the calendar. Consequently, the first day of the year, which is always the first Wednesday after the equinox, is then postponed to the following first Wednesday after the equinox." (also see biblical year).

It is important to realize that intercalations occur in every calendar. No calendar can operate in communion with the seasons without a form of intercalation. 

It is so because a tropical year (the time that the sun takes to return to complete a full cycle) is approximately 365 days, 5 hours, 48 minutes, 45 seconds, which means the mean solar year lasts 365.2421897 days. 

Because 0.2421897 day, or 1/4 of a day, can never be accounted for in any calendar, different types of intercalation have been used through out history and cultures, in order to solve this unavoidable cumulative discrepancy.

For instance, the Gregorian calendar, similar to the Roman calendar, intercalates an average of one day approximately every four years at the end of February. The Jewish lunar calendar, derived from the Babylonian Calendar and similar to the traditional Chinese lunisolar calendar, adds an entire lunar month (Adar II) as needed. Additionally, Egypt intercalated its own set of days at the end of the calendar year when necessary. If a calendar does not intercalate, such as the Hijri Muslim calendar, it inevitably drifts year after year, gradually falling out of sync with the seasons. This is precisely why intercalation has been a common practice in all advanced calendars.

Epagomenal intercalations were particularly well known in ancient cultures, while remaining seldomly documented. Being perceived to be days "outside of time", they were usually not counted, and not specified in calendar displays.

Similarly, no straightforward texts the listing the hebraic epagomenal weeks have survived. However, the intercalation of this united block of 7 extra days can hardly be contested for it naturally occurs when the first day of the year is placed on the 1st Wednesday after the spring equinox, therefore keeping the seasons in sync. It is also note worthy that the reconstruction of the moon cycles as recorded in the priestly cycle scrolls brings further evidence of the hebraïc epagomenal week intercalation in the 1st century.

Thanks to this easy and spontaneous intercalation system of 7 extra days, the Perpetual 364-day Calendar remains one of the most performant methods of dividing the year while staying in a remarkable close synchronization with the seasons (maximum 6 days away from the tropical year).  

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