Short answer: Yes—ideally, to do proper Navkarsi (Navkarshi) next morning, you should observe Chovihār the previous evening.

• What this means:

- Chovihār: after local sunset, no food and no water until next day. - Navkarsi: first intake only 48 minutes after sunrise.

• How to do it correctly (simple steps):

1) Before sunset on the previous day, take pachchakkhān (vow) for Chovihār and next day’s Navkarsi. 2) Finish your last sip of boiled/filtered water a little before local sunset. 3) At sunrise next day, wait 48 minutes; then you may take boiled/filtered water and your first food.

• Tradition notes:

- Śvetāmbara and Digambara both keep “no water after sunset”; daytime water should be properly filtered (and often boiled). The above procedure is accepted in both.

• If Chovihār was missed:

- The full spiritual purity of Navkarsi is considered incomplete. Take fresh pachchakkhān as per your tradition/guru’s guidance and follow from that point onward.

For more, see:

• Navkarsi nu Pachkhan
• Chovihar water timing (what to stop and when)
• Do we need to do Chovihar for Navkarsi?