Tamil New Year is an auspicious day for all Tamilians and the Tamil New Year information should be at your fingertips to understand the actual essence of Tamil New Year.
The information of Tamil New Year goes like this -
The Earth travels in an eliptical pathway round the Sun through 360 degrees (Paakai in Tamil), and the time taken to complete one full round by the Sun (Suriyan in Tamil) in known as a Year (Aandu in Tamil). The circumference of the eliptical path traced by the Earth (Ulaham in Tamil) has the Sun as the main focal point and is divided into twelve arcs. The angular sections traced by each of those twelve arcs with a measurement of 30 degrees are known as a House (Veedu in Tamil or Rasi in Sanskrit). Thus we conclude that the earth passes through twelve Houses in an entire year. Actually, it is the Earth which enters each House at a particular point of time.
But those who live on the Earth, it seemingly appears that the Sun is moving with a relative motion, and we very insecurely state that the 'Sun travels through the twelve Houses'.
The Sun, which seemingly appears to move, in to Meda Veedu or Raasi, is considered to be the starting point of its next total cycle through the twelve Veeduhal.
The period of journey of the Sun in each Veedu or Raasi is termed as a "Thingal"- a Month (also known as Matham in Tamil). Therefore for the Sun to travel through the twelve Veedus or Rasis for completing one entire cycle, it takes twelve Thingals, otherwise known as an "Aandu" - a Year (also known as Varudam in Tamil and Varusha in Sanskrit). The moment the Sun enters the "Meda Veedu" or Raasi was conventionally considered to be the starting point of the New Year by the Tamils.
The "positioning" (Niyathi) of the twenty seven "Meengal" (Natchaththirams) in these twelve Veeduhal has been customarily counted from "Acchuvini" the first Meen in the Meda Veedu. That ends up in "Revathi" as the last Meen in the Meena Veedu. The information that the Meda Veedu begins with the first of the twenty seven Meenkal viz. the Acchuvini in 'position' (Niyathi), too validates that from the early days Tamils considered the starting point of a year cycle with the Meda Veedu. The one who computes the movements of the Earth, Sun, and other Planets in respect of the 12 Veedus or Rasis is known as the "Sothidar".