How is the barsi date calculated — tithi or English calendar?

Barsi is always calculated by the Kshaya Tithi — the lunar tithi on which the person died — not the English calendar date. For example, if a person died on Ashadha Krishna Tritiya, the Barsi falls on the next Ashadha Krishna Tritiya, regardless of the Gregorian date. In a year with an Adhik Maas (leap month), use the second occurrence of that month — the original month, not the added one. If the tithi falls during a severe dosha period, the family Kulapurohit may shift the ceremony to the nearest auspicious tithi within the same lunar month under applicable panjika rules.