In response to popular demand (one person asked), I have written a quick post on the meaningfulness of celebrating Tamil New Year's day on the First day of Chithirai month, which is the Sidereal Vernal Equinox day. I had written a similar post in Tamil few years back and hence the English version now.
day and night are of equal duration. dates are slowly variable across centuries. currently equinoxes occur around March 22 - Spring Equinox and Sept 22 - Autumn Equinox
days when sunlight is longest (Summer Solstice - June 22) and shortest (Winter Solstice - Dec 22)
The Earth revolves around the sun at an inclination of abt 23 degrees. So Sun appears to move up or down thru the year. One revolution is ofcourse a year.
Spring Equinox - sun is directly above the Equator - day and night times are equal on March 22. After this day, Sun starts 'going' north.
Summer Solstice - Sun is farthest from the Equator in the northern direction. its now directly above the Tropic of cancer. Tropic of Cancer passes thru Central India. So summer is intense. Naturally the longest day of the year occurs on June 22nd. Sun now turns back and travels south.
Autumn Equinox - Sun has come back to to the top of Equator. day and night times are again equal on Sept 22.
Winter Solstice - Sun is farthest from the Equator in the Southern direction. Farthest from India. Its now directly above the tropic of capricon in the Indian Ocean. Sun is far, so winter is cold. The shortest day of the year occurs on Dec 22nd.
Note: all these seasons are w.r.t to Northern Hemisphere. In the southern hemisphere, the seasons will be opposite.
Why shud new year be celebrated on Equinox?
There is no necessity, but many cultures do. A day with equal day-night seems a good candidate. Especially most parts of India celebrate on the Spring Equinox. The Roman calendar also began in March with September (Septa - 7), October (Octa - 8), November (Nova - 9), December (Deci - 10) and ending in the last Month February (less days). But the New Year was moved to January for political reasons. Chinese New Year is supposed to be mid-way between Winter Solstice and Spring Equinox. Hence between Jan end to mid Feb.
Equinox is on March 22, why does Tamil New Year occur on April 14?
Becos Tamils (along with malayalis, punjabis, assamese etc) follow Sidereal year and not tropical year. Sidereal is calculating the movement of the Sun vis-a-vis Earth by noting the postion of certain stars. i.e. with respect to fixed positions on the sky and not just the position of the sun. This fixed year is the Sidereal year.
From around April 14, Chitra star (one point of reference) is visible. The Sun is in the Aries (Mesham) zodiac constellation. If we strictly go by the position of the Sun, that year is tropical year. So currently, tropical Equinox is March 22 and sidereal equinox is April 14.
So then, is Ugadi (Telugu/Kannada new year) the correct observance of Spring Equinox?
Not really. They follow a luni-solar calendar. i.e. their months take both the Sun and the Moon into consideration. Their Ugadi (new year) day keeps moving w.r.t the lunar month closer to the Spring Equinox (March 22).
What is Zodiac?
Its just a way of dividing the sky into 12 equal parts and taking a constellation to name it. When the Sun appears within/closer to a constellation of stars, Sun is supposed to be present in that Zodiac. There is no reason to be alarmed about Astrology w.r.t to Zodiac signs.
I don't believe the position of the stars in any year with respect to their position at your time of birth has any relevance. In short, astrology is mostly non-sense. But Zodiac is just a position of the Sun in the sky. So no harm in using the Zodiac signs in conversation.
Coming back, why can't we celebrate New Year on Pongal?
Becos Pongal is already celebrated on Winter Solstice. Sun is turning north from Tropic of Capricon. So its gonna come back to Northern hemisphere, bringing warmth with it. Hence we celebrate. We can as well celebrate both Spring Equinox (as new year) and Winster Solstice as Pongal. More the merrier.
Isn't Pongal the Tamizhar Thirunal (Tamil people's day)?
non-sense. Winter Solstice is celebrated in almost all the states of India. Everywhere its the harvest festival. The joy of Sun starting the northerly journet bringing Spring. And in many states rice-moong dal Pongal (aka Kichidi) is the specialty. This day btw is called Makara Sankranthi becos the Sun travels from the Makara line (Tropic of Capricorn) towards north from this day.
Why can't we have Thiruvalluvar Year and Thiruvalluvar Day as reference for New Year?
How do we know Thiruvalluvar was born on that year? What evidence? Its mere conjecture by Maraimalai Adgigal (aka Vedachalam) that the author of Thirukural was born 31 years before Christ. A dubious assertion which shud not be taken seriously.
And Thiruvalluvar day was selected by Karunanidhi as the day after Pongal, which incidentally is based on the same Tamil calendar which picks Sidereal Vernal Equinox day (Chithirai 1) for New Year. An arbitrary year and arbitrary day as Thiruvalluvar's birth day is quite silly. That day cannot be the start of our year.