Vrishabha Sankranti marks the Sun's entry into Vrishabha, the second sign of the sidereal zodiac, corresponding to Taurus. It is determined by the Sun reaching a longitude of thirty degrees against the fixed stars, computed with the Lahiri ayanamsa, and normally falls in mid-May.
Like the other sankrantis this is a solar event: it turns on the Sun's position along the ecliptic, not on a lunar day or the Moon's phase, which is what distinguishes it from the lunar-month festivals. The transit instant is converted to local clock time, so the calendar date and the timing of any ritual bath or charitable gift can differ by a day from one city to another.
The day opens the month called Vaikasi in the Tamil calendar and Jyeshtha in several regional solar calendars, and in Odisha and parts of the east it is observed with bathing rites and offerings for the well-being of the household.