Chauvihar in January follows the same basic rule every day: after local sunset, do not take any food or drink until the next sunrise. The exact times depend on your city’s sunset and sunrise, so you should check your local Jain calendar or panchang for the precise hours each day. In practice, many communities also observe that the last intake happens a few minutes before sunset to be safe, and the next intake starts after sunrise. This is the standard practice described for Chauvihar and related upavāsa in Jain tradition. If you want the formal wording and a quick comparison with Tivihar, you can read more here