Page:The Burmese & Arakanese calendars (IA burmesearakanese00irwiiala).pdf/38

91. The difference of longitude between sun and moon is found by didi. A didi is the time in which the mean moon increases her longitudinal distance from the mean sun by 12 degrees. The didi elapsed from mean new moon next before Ata Ne to the midnight indicated by the given Thokdadein equal the sum of yet-lun and its fraction plus Thokdadein reduced to didi. That is to say

$D=Y+{\frac {W}{692}}+T(1+{\frac {11}{692}})=Y+T+{\frac {11T+W}{692}}$.

92. Having found the sum of didi, divide by 30, and reject the quotient, as it represents complete lunations, and at every new moon the difference of longitude between sun and moon is zero. The remainder multiplied by 12 is degrees of longitude.

93. The remainder of ${\frac {11T+W}{692}}$ is the awaman of the day. If it be denoted by $Wd$, then the increase of difference of longitude during the fraction of a didi is, in minutes,

$Wd+{\frac {7Wd}{173}}$.

Reduce it to degrees and minutes by dividing by 60.

94. Add together the sun's longitude and the two parts of the difference between sun and moon. Subtract from the sum 52 minutes. The result is the moon's longitude.

95. Add the week-day figure of Ata Ne to the Thokdadein of Second Wazo Labyi. Divide the sum by 7. The remainder indicates the day of the week of Second Wazo Labyi. The sequence of this day from watat to watat ought to agree with the table in paragraph 77.

96. If the moon's longitude as calculated does not lie within Athanli, a day may be added or subtracted, provided it does not set the week-day wrong. That is to say, if the increase of week-day indicates a wangètat one day may be added; if it indicates a wagyitat one day may be subtracted. Thus, in 1234 the increase of week-day since 1231 as obtained from the Thokdadein was 0, indicating a wangètat. The moon's longitude as calculated was 254° 32′, falling short of Athanli. One day was added to the Thokdadein, making the year a wagyitat, with week-day increase 1. The same occurred in 1245, when the calculated moon's longitude was 261° 10′. In 1261 the calculated longitude was 276° 24′, and increase of week-day 1, indicating a wagyitat. One day was deducted, making a wangètat. The object of this is not apparent, as the moon's longitude often exceeds Athanli. These are the only occasions on which a correction has been applied to the calculated Thokdadein for Second Wazo Labyi since 1215 B. E.