The Bris of a child in good health should be held on the eighth day after his birth. The Jewish calendar changes days at sundown, with the evening assigned to the following day. Thus, for example, if the child was born on a Tuesday afternoon, the Bris would be ideally scheduled for the following Tuesday. However, if he was born on Tuesday night (which is considered by the Jewish calendar to be the beginning of Wednesday), the Bris would be scheduled for the following Wednesday.
Contrary to the practice for most other Jewish life cycle ceremonies, the Bris supersedes many Sabbath and holiday restrictions. (However, certain prerequisites do apply.) On the other hand, if there is any question about the health of the newborn child, the Bris is delayed until the child's doctor and the mohel agree that there is no longer any danger to the child. The Bris must be performed during the day, anytime from sunrise to sunset. It may not take place at night.
A Bris may not be performed before the eighth day under any circumstances.