Names of the days of the week which is mainly based on a medieval version of Spanish, the five days of Monday–Friday closely follow the Spanish names. Sunday uses the Arabic name, which is based on numbering, because a Jewish language was not likely to adapt a name based on "Lord's Day" for Sunday. As in Spanish, the Ladino name for Saturday is based on "Sabbath". However, as a Jewish language—and with Saturday being the actual day of rest in the Jewish community—Ladino directly adapted the Hebrew name, "Shabbat". From Latin "Dominicus (Dominica)" or Greek Κυριακή (Christian Sabbath) After No Work. In Russian also "Day After Week(end)"
Eight-day week popularity of the seven-day rhythm won and the eight-day week disappeared. The cycle of seven days, named after the sun, the moon, and the five planets visible to the naked eye, was already customary in the time of Justin Martyr, who wrote of the Christians meeting on the Day of the Sun (Sunday). Emperor Constantine eventually established the seven-day week in the Roman calendar in AD 321. The Celts used periods of darkness such as night and winter to begin their calculations of time. This meant that the first period of time in a "week" was a night, followed by