Many people in South India celebrate Yugadi on 14th of April every year. This includes districts from coastal Karnataka as well.

You may wonder  how this festival falls on the same day everyday? This is because it is a festival based purely on the solar calendar – instead of the luni-solar calendar which is used to calculate the date the dates for most other Indian festivals.

This is the day when the Sun enters mESha rAshi (Aries). But if you are used to read your predictions from the newspapers everyday, I’m sure you’d have noted they assign Aries to those who are born between March 21st to April 21st.

So where is the catch? Who is right?

Both :), in their own ways.

The year used to be calculated from the Vernal Equinox. Back in that time when constellation boundaries were drawn, the Vernal Equinox also coincided with the time when Sun entered the boundary of Aries and hence the Zodiac begins with the constellation Aries. This point (where the ecliptic, and the celestial equator crossed each other was termed the “First point of Aries”, since it actually was close to the beginning of this constellation boundary. This was made the starting point (zero degrees) for all celestial calculations.

Due to precession, Vernal Equinox falls behind (in time) every year and now it occurs around the 20th/21st of March. The western astronomy found a way to get out of this problem by moving this reference point, and so the “First point of Aries” does not occur near the real boundary of the constellation Aries. However, it is still called by the same name, and causes some confusion. By doing this, the Vernal Equinox, always falls at the time when the Sun is at the “First point of Aries”.

Indian astronomy, on the other hand,  does not move the reference point for the calculation of festivals. Hence, the mESha sankramaNa is celebrated on the day Sun enters the real boundary of Aries,  and not when the Sun is at the “First point of Aries”. The equinox and the beginning of the year have been thus de-linked.

Here are couple of sky simulations showing the position of the Sun, around these days.

Around March 20th,2009 – Beginning of the ‘tropical’ year

Around March 20th,2009 - Near Vernal Equinox

Around March 20th,2009 - Near Vernal Equinox

Around April 13th, 2009 – Near the beginning of the traditional Indian solar year:

Solar position near the beginning of Indian solar new year

Solar position near the beginning of Indian solar new year