By Swami Harshananda
Nirayana literally means ‘neglecting the precession of the equinoxes’.
An equinox is the point where the sun crosses the plane of the earth’s equator. There are two equinoxes:
- The vernal equinox on March 21
- The autumnal equinox on September 22
On these two days, the length or the duration of the day and the night are exactly equal.
In the traditional calendars called ‘paṅcāṅgas’, the precession of the equinoxes due to the wobbling movement of the earth is not taken into account. Hence this system of calculation is known as nirayana whereas, if taken into account, it is called śāyana.
Calculation of Nirayana
Though the actual date of the vernal equinox at present is 21st March, it is considered as 13th April ignoring the precession. In order to remove this anomaly, the National Calendar was adopted in 1957. March 22 was reckoned as the 1st Caitra-Śaka era 1879. The duration of the year adopted for calculations taking the ayana or precession into account was 365.2422 days.
- It was recommended by the Calendar Reform Committee.
- The Concise Encyclopedia of Hinduism, Swami Harshananda, Ram Krishna Math, Bangalore