The modern Jewish Passover and Feast of Unleavened Bread is seven days, starting with the sunset at the beginning of Nisan 15. Judaism reckons the beginning of each day at sunset, not at midnight as is common in Western reckoning. The Biblical law regarding Passover is said to be a "perpetual ordinance" (Exodus 12:14), also applicable to Proselytes, but what it means to observe Biblical law in Christianity is disputed.