Unlike the Gregorian calendar (31, 30, 28/29), Myanmar months have 29 or 30 days. In a standard year (not a Wat-year ), there are 354 days. However, 1366 was a special year because it contained a Wat-lin (intercalary month) to catch up with the solar cycle.
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For calendar enthusiasts, the most notable feature of the Myanmar year 2004 (1366) was the . Just like the Gregorian calendar adds a "Leap Day" on Feb 29, the Burmese calendar adds an entire month (a second Waso) every few years. 2004 was one of those years. myanmar calendar 2004