The declination of the Sun is computed by the formula
Sin J = Sin L Sin w
where J is the Sun’s declination of that particular date and time, L is the tropical longitude of the Sun and w, the Sun’s maximum declination, which is 23 degrees and 27 minutes.
The Sun’s maximum declination will be reached during Karkyadi ( The First Point of Cancer ) and Makaradi ( The First Point of Capricorn ). At Karkyadi, it will be +23 d 23 m and at Makaradi, it will be -23 d 27 minutes.
And at Meshadi ( The First Point of Aries ) and Thuladi ( The First Point of Libra ), the solar declination will be zero. Days and nights will be of equal duration and hence they are called Equinoxes.
Yada Mesha Thulayo varthathe thada ahoratranam samanani bhavanthi