section_path: History/Early formation
section_name: Early formation
paragraph_text: Early formation
  
  Lunisolar calendars similar to the Hebrew calendar, consisting of twelve lunar months plus an occasional 13th intercalary month to synchronize with the solar/agricultural cycle, were used in all ancient Middle Eastern civilizations except Egypt, and likely date to the 3rd millennium BCE. While there is no mention of this 13th month anywhere in the Hebrew Bible, still most Biblical scholars hold that the intercalation process was almost certainly a regularly occurring aspect of the early Hebrew calendar keeping process.