section_path: History/Leap months
section_name: Leap months
paragraph_text: Leap months
  
  According to Rabbinic Judaism, Exodus 12:1–2 requires that the months be determined by a proper court with the necessary authority to sanctify the months. Hence the court, not the astronomy, has the final decision. When the observational form of the calendar was in use, whether or not a leap month was added depended on three factors: 'aviv, fruits of trees, and the equinox. On two of these grounds it should be intercalated, but not on one of them alone. It may be noted that in the Bible the name of the first month, Aviv, literally means "spring". Thus, if Adar was over and spring had not yet arrived, an additional month was observed.