Vaishakha वैशाख

Each lunar month takes its name from the nakshatra the full moon falls in or near — here, Vishakha. The naming is approximate and drifts slowly with precession, but it is the origin of all twelve names, and it is why the months line up with star groups rather than with the Gregorian calendar.

Vaishakha falls in Vasanta (Spring), which spans roughly mid-March to mid-May. The year opens here. Holi and Vasant Navratri fall in this ritu.

The Gregorian span above is approximate — a lunar month shifts by about eleven days a year against the solar calendar and is pulled back by the insertion of an adhika month every two to three years. If an adhika Vaishakha occurs, there are two of them that year, and the second (nija) one carries the festivals. Our daily panchang computes the current month from the actual position of the Sun at the enclosing new moon, so it is right regardless.