Chauvihar in September means:

• After local sunset, you refrain from all intake—no food and no water—until the next sunrise. This is done to protect night-born beings and to keep saiyam (self-control). In practice, many observe finishing the last bite/sip a few minutes before sunset and resuming after sunrise with careful use of water (typically boiled/filtered as per your tradition). ( jainknowledge.com)
• Digambar and Shvetambar traditions both follow the rule of no water after sunset for Chauvihar; often daytime water is boiled/filtered as a precaution. Some communities may have stricter local rules, but the core idea remains the same. ( jainknowledge.com)

Helpful note for September: the exact times depend on where you are. Check your local sunset on that day and plan to complete your last intake a little before that time, then resume after local sunrise.

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