The 7 Days of the Week
The 7-day week is the international standard week (ISO 8601) used by the majority of the world.
Starts Monday or Sunday
Named After Gods and Planets
The names of the 7 days of the week in most Latin-based languages come from the Roman calendar, which related each day with 7 celestial bodies considered to be gods: the Sun, the Moon, Mercury, Venus, Mars, Jupiter, and Saturn.
The English language has retained the planet names for Saturday, Sunday, and Monday. However, the names for the other days of the week have been replaced by their equivalent Norse or Germanic gods.
Some Asiatic languages such as Hindi, Japanese, and Korean have a similar relationship between the weekdays and the planets.
The 7-day-week provides a clear method of representing dates and times to avoid misinterpretation between people from different countries with varying traditions for writing numeric dates and times.
Why Seven days?
The Romans later replaced these names with their planet gods in the ancient Roman calendar and Germanic and Norse people later did the same with some of their gods.
When Is the Weekend?
As the first day of the week varies in different cultures, so does the weekend. The Christian or Western world marks Sunday as their day of rest and worship, while Muslims refer to Friday as their day of rest and prayer. The Jewish calendar counts Saturday – the Sabbath – as the day of rest and worship.
Both Saturdays and Sundays are common days of rest in the calendar. Calendars in some countries use a separate color for the weekends and reserve the black or gray fonts for the weekdays, Monday through Friday.
52 Weeks & 1 Day
Some Years Have 53 Weeks
The weeks of the year in a Gregorian calendar are numbered from week 1 to week 52 or 53. If a year, and week 1, starts on a Thursday, then the weeks are shifted so that there will be 53 weeks in that year.
These week numbers are commonly used in some European and Asian countries; but not so much in the United States.