section_path: Accuracy
section_name: Accuracy
paragraph_text: Accuracy
  
  The Burmese calendar uses lunar months but tries to keep pace with the solar year. The present Thandeikta system's solar year is about 23 minutes 51.43 seconds ahead of the actual mean tropical year of 365.241289 days. The older Makaranta system was actually slightly more accurate, with 23 minutes 50.87 seconds ahead of the actual year. The table below shows how Thandeikta purports to achieve a narrower difference (hence better accuracy) over Makaranta.
  
  The gain in accuracy is 0.0010391634 day (89.78371776 seconds) over 19 years, or about 4.72546 seconds a year. However, this gain is illusory as Thandeikta achieves the gain by redefining the mean lunar month (lunation), which is then more accurate and the solar year, which is less accurate. The table below shows the solar years of both systems in comparison with the actual mean tropical year. Thandeikta is 0.56 second a year less accurate than Makaranta.
  
  In sum, both systems are about 24 minutes per year ahead of the actual tropical year; the systems' methods of intercalation fixes only their internal error; and Thandeikta slightly accelerates the annual drift. The accumulating error means the New Year's Day, which used to fall near the vernal equinox at its launch on 22 March 638 CE (Julian), fell on 17 April (Gregorian) in 2022—a difference of 23 days. Burmese calendarists have dealt with the issue by using apparent reckoning and periodically modifying the intercalation schedule in the Metonic cycle. One major downside of this approach is that it is difficult to publish future calendars more than a few years (often even a year) ahead.