Hindu Date Converter

A civil day takes the tithi current at its sunrise, and a tithi that holds no sunrise is kshaya. The tithi's start and end are the same instant everywhere; the day it lands on is read from your place's sunrises. Kane, the sunrise tithi: History of Dharmasastra, Vol. V Pt. I p.73 (paraphrased): a day-long observance follows the tithi prevailing at sunrise Kane, kshaya: History of Dharmasastra, Vol. V Pt. I p.69 (paraphrased): a tithi that begins after one sunrise and ends before the next is kshaya

Months are named by the present rule: an amanta month takes its name from the sign the Sun holds when it begins, and a month with no sankranti is adhika. Sewell & Dikshit: The Indian Calendar, Art. 45-46 (adhika and kshaya months, the naming rule), Art. 51 (the purnimanta fortnights), Art. 71 (the eras)

A festival or vrat keeps its own rule - a pradosha, an aparahna, the Ekadashi lineages - so its day can differ from the sunrise day: Festivals · Vrats

The other way round - the Hindu date of any civil day - is the Panchang for that date. Open the Panchang