sunday comes first in order in calendars shown in the table below. in the judeo-christian or abrahamic tradition, the first day of the week is sunday. biblical sabbath (corresponding to saturday), when god rested from , made the day following sabbath the first day of the week (corresponding to sunday). seventh-day sabbaths were sanctified for celebration and rest. after the week was adopted in early christianity, sunday remained the first day of the week, but also gradually displaced saturday as the day of celebration and rest, being considered the lord's day.