of the epact are correctly calculated they must agree. By Makaranta the adimath thetha is not correct, because the ratio assumed between the lengths of a mean solar month and a mean lunation, 235 : 228, is only a rough approximation; its error is the error of the Metonic cycle. In the first cycle of Poppasaw's era both forms of the epact pyoed in the same year, except in the 8th year when the adimath thetha was slightly in arrear. In the 12th century the error had accumulated so much that adimath pyo was behind yet-lun pyo every time. Thus
| Yet-lun pyo | 1101 | 1104 | 1107 | 1109 | 1112 | 1115 | 1117 |
| Adimath pyo | 1102 | 1105 | 1108 | 1111 | 1113 | 1116 | 1119 |
In five cases the adimath pyo was one year behind, in the other two cases it was two years behind. Later in the century the error was greater, thus
| Yet-lun pyo | 1177 | 1180 | 1182 | 1185 | 1188 | 1191 | 1193 |
| Adimath pyo | 1178 | 1181 | 1184 | 1187 | 1189 | 1192 | 1195 |
In three cases the adimath pyo was two years behind. Thandeikta corrected adimath thetha and made it agree with yet lun.
112. To make the month in which Ata Ne occurs Tagu, and the month in which the full moon is in Athanli Wazo or Second Wazo, the watat year should be, not yet-lun pyo year as stated in Thandeikta, but the year before yet-lun pyo, or approximately every year in which yet lun exceeds 19. This was so at the beginning of the era. After 12 centuries we find 6 watat occurring in yet-lun pyo year and the seventh in the year after yet-lun pyo (year 5—expired—of cycles, 61, 62 and 63, viz., 1145, 1164 and 1183). In cycle 64 this last error was corrected at Amarapura by placing the watat in year 4 (1201) instead of year 5 (1202). The subsequent corrections of the Metonic cycle, namely the changes
| from 2 to 1 in 1217 |
| from„ 13 to„ 12 in„ 1228 |
| from„ 10 to„ 9 in„ 1263 |
have placed watat in the year before yet-lun pyo, but only when the yet-lun amounts to 27, 28 or 29. It seems to have been considered that to revert fully to the original rule, and place watat always in the year before yet-lun pyo, would be too drastic a measure, as it would place the beginning of Lent on the average five days later in the season than it is now. It is already fifteen days later in the season than it was in Poppsasaw's time.
113. From these facts it is clear that
(a) The error of the Burmese solar year is constantly moving the nekkat Athanli later and later in the seasons,
