Choviyar upvas lasts from after the sunset of a day until the next sunrise. In practice, this means roughly a 12–14 hour window (the exact duration depends on your location and the time of year). Some communities may have slight differences in the cut-off time for starting or ending the vow, but the core idea is: no food or drink after sunset until the next day’s sunrise.

• It is considered a strong form of restraint, focusing on ahimsa, self-control, and inner purification.
• Digambar and Śvetāmbara traditions both practice chovihār, with only minor procedural variations guided by one’s guru or local tradition.

You can read more about chovihar upvas here