Rāi (night) Pratikraman should be done after sunset.

• Ideal time: within one muhūrta (about 48 minutes) after sunset.
• If you miss the ideal time: complete it the same night before sleeping; do not carry it to the next day.

Tradition notes:

• Shvetāmbara: many follow the above; some lineages allow up to two muhūrtas after sunset. Follow the maryādā of your gacch/saṅgh.
• Digambara: generally to be done soon after sunset, preferably within one muhūrta.

Always keep bhāva (pure intention) and avoid eating/drinking after sunset before doing Rāi Pratikraman.