Kanya Sankranti marks the Sun's entry into Kanya, the sixth sign of the sidereal zodiac, corresponding to Virgo. It is fixed by the Sun reaching a longitude of one hundred and fifty degrees against the fixed stars, computed with the Lahiri ayanamsa, and usually falls around the seventeenth of September.
This is a solar reckoning, defined only by the Sun's place on the ecliptic and independent of the lunar months that carry festivals such as Navratri or Diwali. Because the transit instant is stated in local clock time, the observed date can move by a day between cities, and associated bathing and giving follow the nearest sunrise.
In eastern and northern India the day is widely kept as Vishwakarma Puja, when craftspeople, engineers and factory workers honour Vishwakarma, the divine architect, and worship their tools and machines. In the Tamil calendar it opens the month of Purattasi, a period of Vishnu worship.