In popular practice, the bride and the groom have a special arrangement where they engage in sexual activity on the very first night at a pre-determined auspicious time. It depends upon which Grhya Sutras the locality and family follows. Majority of the North Indians follow Shukla Yajurveda, so they do it on 4th day after Vivaham (marriage).
In customary practice, the bride and groom engage in sexual activity on their first night at a designated auspicious time. This timing can vary based on religious texts followed by the family and locality. Most North Indians adhere to Shukla Yajurveda and perform this ritual four days after marriage.