In Navkarshi Pachkhan, the standard practice is to have your last meal before sunset on the previous day. After sunset, you observe the fast (upvas) and do not eat for the rest of the night and the following day until the next morning (sunrise) in most common interpretations.

Notes:

• The exact cut-off time depends on local sunrise/sunset times, so use your area’s local sunset as the fasting start time.
• Some communities permit drinking water during the fast, while others observe a stricter fast without water. There are small differences between Digambar and Shwetambar practices.
• If you’re following a particular temple or community rule, check their specific guidance, as there can be slight regional variations.

If you’d like, tell me your city or temple tradition, and I can provide a more precise timing based on that tradition.