How these times are worked out
Every pachkhan time is counted from the day's own sunrise, so it changes a little each day and differs from city to city. The day between sunrise and sunset is divided into four prahars (quarters).
- Navkarsi (नवकारसी): 48 minutes after sunrise, the earliest time food or water is taken after the night's vow.
- Porsi (पोरसी): one prahar, a quarter of the daylight, after sunrise.
- Sadh Porsi (साढ़ पोरसी): one and a half prahars after sunrise.
- Purimaddh (पुरिमड्ढ): two prahars, midday, when half the daylight has passed.
- Avaddh (अवड्ढ): three prahars after sunrise.
- Chauvihar and Tivihar: sunset. After it, no food until the next Navkarsi; with chauvihar, no water either.
Sunrise here is the moment the upper edge of the Sun appears, with the usual allowance for the air bending its light, the convention most printed panchangs use. The tithi is the one current at sunrise, which names the whole day.
Your own sangh comes first. Upashrays and gacchas round these times differently, and some add a few minutes of margin. If yours publishes its own times, follow them: the vow is kept with your sangh, not with a website.