No names were used by the Hebrews for the days of the week, except for the seventh day, called the Sabbath. (See SABBATH DAY.) Reference was made to the various days by their numerical order. In the days of Jesus and his apostles, the day preceding the Sabbath was called the Preparation. (Mt 28:1; Ac 20:7; Mr 15:42; Joh 19:31; see WEEK.) The practice of naming the days after the names of the planets and other heavenly bodies was pagan. The Romans named the days after the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn, but in northern Europe, four of these names were later changed into the Germanic equivalents of the Roman gods whom the days represented.

This flexible use of the word “day” to express units of time of varying length is clearly evident in the Genesis account of creation. Therein is set forth a week of six creative days followed by a seventh day of rest. The week assigned for observance by the Jews under the Law covenant given them by God was a miniature copy of that creative week. (Ex 20:8-11)