In Jainism, a fast (upvas) is usually observed from the morning of the fast day and ends when the vow is completed. The common patterns are:

• One-day fast: starts at sunrise and ends at sunset. Some people break the fast after evening prayers or a small, simple meal.
• Longer fasts: can last for multiple days and typically end at the next sunrise after the final day, though some traditions end at sunset of the last fasting day.

Differences between Digambar and Shwetambar:

• Both traditions largely follow the same basic timing (start at sunrise). The main differences you’ll see are in how meals are taken, what is allowed during the fast (water-only vs. food restrictions), and the specific rituals you observe to break the fast. Timing itself—start at sunrise and end at sunset for a short fast, or end at the next sunrise for longer fasts—remains the same in both traditions.

If you have a specific type of fast or a particular tradition in mind (e.g., a particular tithi or festival fast), I can explain that exact pattern more precisely.