Why Do We Have Seven Days in a Week?

Do you have a preferred day of the week? Maybe it’s Monday, as you eagerly anticipate returning to school after a long weekend. Or perhaps it’s Wednesday, because that’s when you have piano lessons. Or could it be Friday, Saturday, or Sunday? Many individuals look forward to the weekend!

Regardless of which day of the week brings you the most joy, we know it must be Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, or Sunday. Those are the only options we have, because a week consists of only seven days. But have you ever wondered why that is?

After all, a typical year consists of 365 days. Why don’t we have 73 five-day weeks? Or 26 14-day weeks? When you think about it, couldn’t we divide those 365 days however we please? So why have we always had seven-day weeks?

The simple answer is because it has been that way for a very long time. The seven-day week can be traced back thousands of years. Historians believe it most likely originated with the ancient Babylonians.

Our other units of time can be explained by natural phenomena, such as the Earth’s rotation, the Moon’s phases, and the Earth’s movement around the Sun. For example, a day is determined by the Earth’s rotation on its axis, a year is determined by the Earth’s movement around the Sun, and months are approximated by the Moon’s phases. However, there is no natural explanation for the seven-day week.

Some experts speculate that the ancient Babylonians may have adopted a seven-day week to correspond with the individual cycles of the Moon throughout the month. However, these cycles only partially align with a seven-day week, requiring the addition of an extra day or two to one week every few months.

So why did the ancient Babylonians choose a seven-day week? Some experts believe it is because they attributed a mystical significance to the number seven. This belief may have been influenced by their focus on the seven celestial bodies known to them at that time: the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn.

The practice of performing rituals every seven days may have led to the establishment of the seven-day week. Additionally, these same celestial bodies may have influenced other ancient cultures, including the Chinese and Japanese, to adopt their own seven-day weeks.

The development of the seven-day week in other cultures can be traced back to the creation story in the Bible. According to the Book of Genesis, God created the world in six days and rested on the seventh day. Many believe that this served as a model for early cultures: work for six days and rest on the seventh day.

Our modern calendars still adhere to the seven-day week. Scholars believe that its formal adoption by Roman Emperor Constantine in 321 solidified its global acceptance. Constantine designated Sunday, the Christian Sabbath, as the first day of the week and Saturday, the Jewish Sabbath, as the last day of the week.

Many calendars and cultures around the world still consider Sunday to be the first day of the week. However, in practice, with the modern five-day work week and two-day weekend, many people informally regard Monday as the first day of the week and Sunday as the last.

Give It a Try

Are you eagerly anticipating the weekend? While you wait, make sure to explore the following activities with a friend or family member:

Imagining a Different Calendar

Have you ever wondered what it would be like if the calendar didn’t have seven days? What if it had five, ten, or even fifteen days? Can you imagine going to school or work for eight or thirteen days before getting a two-day weekend? Take a moment to think about how your life would be different if the week had a different number of days!

Now, let’s take it a step further. If you had the chance to create a brand new calendar, how would you do it? Get a large piece of paper and mark a symbol for each of the 365 days in a year. Then, let your imagination run wild and come up with your own unique way of dividing those days into weeks and months.

Have you ever noticed that certain days seem to have a different feel to them? For example, Mondays might feel different from Fridays. But what about Tuesdays? Talk to your friends and family about the different feelings they associate with each day of the week.

Wonder Sources

  • http://www.almanac.com/content/why-week-has-seven-days
  • http://www.bbc.co.uk/religion/0/20394641
  • http://www.todayifoundout.com/index.php/2013/04/the-origin-of-the-7-day-week-and-the-names-of-the-days-of-the-week/


1. Why are there seven days in a week?

The concept of a seven-day week dates back to ancient civilizations, including the Babylonians and the ancient Egyptians. The Babylonians, who were skilled astronomers, observed seven celestial bodies – the Sun, the Moon, Mars, Mercury, Jupiter, Venus, and Saturn. They associated each celestial body with a god and named each day of the week after these gods.

2. How did the names of the days of the week originate?

The names of the days of the week originated from various mythologies and cultures. For example, Sunday is named after the Sun, Monday after the Moon, and Saturday after Saturn. Tuesday is derived from the Old English word “Tiwesdæg,” named after the Norse god Tyr. Wednesday comes from “Wōdnesdæg,” named after the Norse god Odin. Thursday is named after the Norse god Thor, and Friday after the Norse goddess Frigg.

3. Why is Sunday considered the first day of the week in some cultures?

The choice of Sunday as the first day of the week varies across different cultures and calendars. In some cultures, Sunday is considered the first day due to religious reasons. For example, in Christianity, Sunday is considered the day of rest and worship, commemorating the resurrection of Jesus Christ. In other cultures, Monday is considered the first day of the week, aligning with the start of the workweek.

4. Have there been any attempts to change the number of days in a week?

Throughout history, there have been some attempts to change the number of days in a week. The French Revolution, for example, introduced a ten-day week called the “French Republican Calendar” in 1793. However, this calendar was not widely accepted and was eventually abandoned. Similarly, there have been proposals to adopt a six-day week or a decimal-based calendar, but these ideas have not gained widespread traction.

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