Mostly a south Indian festival, Vishu is the dawn of the new astronomical year
, and the day marks the first day of the Malayalam month of Medam, which corresponds with April in the Gregorian calendar.
In the tutorial on seasons I find, "Our seasons are the four quarters of the astronomical year
, depending on the apparent solar ecliptic in the celestial sphere.
In England until 1751, the year began on Lady Day, 25 March, following ecclesiastical practice, but the astronomical year
began on I January, following the old Roman reckoning.