Apna Panchang gives the daily Hindu almanac for Indian cities: tithi, nakshatra, yoga, karana and vara, together with sunrise, sunset, moonrise, moonset, Rahu Kaal, Yamaganda, Gulika Kaal, the Choghadiya table and the Abhijit and Brahma muhurats.
How it is calculated
Nothing here is typed in by hand or copied from a printed almanac. Positions of the sun and moon are computed from the standard astronomical series, converted to sidereal longitudes on the Lahiri ayanamsa, and read at the moment of sunrise for the city you choose. Tithi is the moon's elongation from the sun divided into twelve-degree steps; nakshatra and yoga divide the sidereal circle into twenty-seven. Rahu Kaal, Gulika, Yamaganda and the Choghadiya are the eighths of the day and night between sunrise and sunset, assigned by weekday in the usual order.
Why your city matters
Sunrise in Kolkata and sunrise in Ahmedabad are nearly an hour apart. Everything that hangs on sunrise hangs on it everywhere, so a panchang quoted for one city is simply wrong in another. Pick yours rather than taking the default.
Where we are careful
Against the established almanacs our figures land within about a minute: sunrise and sunset usually to the second, tithi, nakshatra and yoga occasionally a minute either way. That gap is real and we would rather name it than pretend otherwise — it comes from how finely each almanac carries the lunar theory and the ayanamsa, and no two of them agree exactly either. Moonrise and moonset can differ by three or four minutes, because they also depend on the moon's parallax and on which point inside a city is taken. Rahu Kaal, Gulika, Yamaganda and the Choghadiya are pure arithmetic on sunrise and sunset, so they are as close as the sunrise itself.
What this is not
It is a calculation, not a ruling. Fasts, festivals and the choice of a muhurat are decided by tradition, by regional practice and by your own priest, and those can legitimately differ from the arithmetic. Where a date is disputed, ask rather than assume.