In Jainism, "navkarsi" refers to the first meal taken at least 48 minutes (one prahar or approximately 1 hour 12 minutes, depending on the tradition) after sunrise. According to Jain discipline, especially among Shravaks (lay followers) and Shramans (monks/nuns), there is a practice of avoiding intake of food and water during the night, starting from sunset.

On the previous day before navkarsi, water intake is to be stopped at the time of sunset (Sandhya Kaal). This means that after sunset, both food and water are to be completely avoided until the next day's navkarsi.

This practice aligns with the Jain principle of Ahimsa (non-violence), as consuming food and water after sunset increases the possibility of harming micro-organisms that become more active at night.

In summary: On the previous day of navkarsi, you should stop taking water at sunset and resume only after performing navkarsi the next morning.