In Jainism, the basic idea of day and night follows the same traditional Indian timekeeping used in many dharmic texts.

• A full day and night together make one aho-ratra (24 hours).
• Each day (and each night) is divided into 4 equal parts called prahars. So a 24-hour cycle has 8 prahars in total: 4 during the day and 4 during the night.
• In the common unit system, one ghati is 24 minutes. Since a day is 24 ghatis, one ghati equals 24 minutes, and a prahar is 3 ghatis (72 minutes). The eight prahars together fill the 24-hour cycle.

Important notes:

• The starting point for marking day and night is the Sun’s apparent motion: day runs from sunrise to sunset, night from sunset to sunrise. This is the standard convention found in Jain practice.
• Muhurtas (smaller time blocks) are used in Jain rituals and observances, with each day-night cycle subdivided into 30 muhurtas in some calculations. Prahar and muhurt timings can be used to plan fasting, prayers, and rituals.
• There is no essential doctrinal difference in day-night calculation between the Digambar and Shwetambar traditions on this point; both follow the same core timekeeping framework.

If you’d like, I can outline how the timings are used for common Jain observances (like starting/ending fasts) in simple step-by-step examples.