during the Buddhist Lent, have been replaced by newer Burmese names (Waso, Wagaung, Thadingyut), which used to mean just the Full Moon days of the three months. In great leap years, the month of Nayon gets an extra intercalary day called yet-lun () or yet-ngin () and has 30 days. In the Arakanese calendar, the month of Tagu gets the extra intercalary day in great leap years. Year Types of astronomical year The calendar recognises three types of astronomical year: tropical year, sidereal year and anomalistic year. Types of calendar year The Burmese calendar is a lunisolar calendar in which the months are based on lunar months and years are based on solar years. One of its primary objectives is to regulate the lunar part that it will keep pace with the solar part. The lunar months, normally twelve of them, consist alternately of 29 days and 30 days, such that a normal lunar year will contain 354 days, as opposed to the solar year of ~365.25 days. Therefore, some form of addition to the lunar year (of intercalation) is necessary. The overall basis for it is provided by cycles of 57 years. Eleven extra days are inserted in every 57 years, and seven extra months of 30 days are inserted in every 19 years (21 months in 57 years). This provides 20819 complete days to both calendars. As such, the calendar adds an intercalary month ( ) in leap years ( ) and sometimes also an intercalary day ( ) in great leap years ( ). The intercalary month not only corrects the length of the year but also corrects the accumulating error of the month to extent of half a day. The average length of the month is further corrected by adding a day to Nayon at irregular intervals—a little more than seven times in two cycles (39 years). The intercalary day is never inserted except in a year which has an intercalary month. The Hindu calendar inserts an intercalary month at any time of year as soon as the accumulated fractions amount to one month. The Burmese calendar however always inserts the intercalary month at the same time of the year, after the summer solstice while the Arakanese calendar inserts it after the vernal equinox. The actual calendar year (Wawharamatha Hnit, ) consists of 354, 384 or 385 days. The Thai Chulasakarat calendar uses a slightly different