section_path: Accuracy/Metonic cycle drift
section_name: Metonic cycle drift
paragraph_text: Metonic cycle drift
  
  A larger source of error is the inaccuracy of the Metonic cycle. Nineteen Jewish years average 6939d 16h 33m 03 1 ⁄ 3 s, compared to the 6939d 14h 26m 15s of nineteen mean solar years. Thus, the Hebrew calendar drifts by just over 2 hours every 19 years, or approximately one day every 216 years. Due to accumulation of this discrepancy, the earliest date on which Passover can fall has drifted by roughly eight days since the 4th century, and the 15th of Nisan now falls only on or after 26 March (the date in 2013), five days after the actual equinox on 21 March. In the distant future, this drift is projected to move Passover much further in the year. If the calendar is not amended, then Passover will start to land on or after the summer solstice around approximately AM 16652 (12892 CE).