Names of the days of the week

We have seven days in a week.

Long ago, people named days after things in the sky. They used names for the sun and the moon. They also used names for the planets.

Many names came from the Romans. They named days after their gods. For example, Tuesday is named for Mars. Mars was a god of war.

Other people used their own gods. The Germanic people used a god named Thor. They named a day after him.

Some people call Monday the first day. Other people say it is the second day. This can change by land.

It is fun to see how names change. Our days help us track time.

Have you ever wondered why our days have such strange names? Most languages use a seven-day week. This system began a long time ago. The Babylonians may have started it 4,000 years ago. They thought the number seven was sacred.

Many names come from the sky. People named days after the sun and the moon. They also used the names of planets. In the Roman Empire, days were named after Roman gods. For example, Tuesday was the day of Mars. Mars was a god of war. Thursday was named for Jupiter. Jupiter was a god of thunder.

Other groups used their own gods. The Germanic people changed the Roman names. They used their own gods instead. They named Thursday after Thor. Thor was a god of thunder. They also named Tuesday after Tiw. Tiw was a god of combat. Some people call Monday the first day. Others say it is the second day. This depends on where you live. It is a big part of how we track time.

Have you ever wondered why our days have such strange names? Most people use a seven-day week to track time. This system is very old and comes from ancient civilizations. Many historians believe the Babylonians started using a seven-day week about 4,000 years ago. They believed the number seven was a sacred number.

This idea moved from the Sumerians to the Babylonians. Later, the Roman Empire adopted the system during late antiquity. The seven-day week eventually spread through many Christian cultures around the world. It even replaced an older Roman system called the internundinum.

Many day names come from the sky and the planets. In many languages, the names come from seven heavenly bodies. These are the Sun, the Moon, Mars, Mercury, Jupiter, Venus, and Saturn. In the Greco-Roman tradition, these bodies were linked to specific gods. For example, Sunday is the day of the Sun. Monday is named after the Moon. Tuesday is the day of Mars, the Roman god of war. Wednesday is named for Mercury. Thursday belongs to Jupiter. Friday is named for Venus. Saturday is named after Saturn.

Different groups of people changed these names over time. The Germanic peoples used a process called interpretatio germanica. They took the Roman system but swapped the gods for their own. They did this between 100 AD and the 7th century. For instance, they named Thursday after Thor, a god of thunder. This matched the Roman day of Jupiter, who was also a thunder god. They named Tuesday after Tiw, a god of combat. This was their version of the Roman god Mars. They also named Wednesday after Woden, a god of magic and knowledge.

Languages have many different ways of saying these names today. Most Romance languages kept the Latin names for most days. However, many changed Sunday to mean "the Lord's Day." In Portuguese, they use numbers for weekdays but keep special names for the weekend. In Welsh, people do not just say the day name. They add words for "morning," "night," or "afternoon" to the name.

Even constructed languages like Esperanto use these ancient roots. They often take names from French to build their words.

How we count the week can change depending on where you live. The international standard ISO 8601 says Monday is the first day. However, many other countries count Monday as the second day. In some places, Sunday is still seen as the first day. This is because it was once the day of the sun god, Sol Invictus. Even though the names and starts change, the seven-day pattern stays the same. It is a way for people all over the world to share time.

The names of the seven days of the week represent a deep connection between human timekeeping and the heavens. Most modern languages use a seven-day cycle to organize life. This system is not a recent invention. Historians believe the Babylonians began using a seven-day week approximately 4,000 years ago. To the Babylonians, the number seven held sacred significance. This method of tracking time moved from the Sumerians to the Babylonians. Eventually, the Roman Empire adopted the system during late antiquity.

The mechanism behind these names involves a link between days and celestial bodies. Many languages derive their weekday names from the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn. These seven heavenly bodies were associated with specific deities in Hellenistic astrology. The order of these days is often tied to the Ptolemaic system of planetary spheres. This system asserts a specific order of heavenly bodies from the farthest to the closest to the Earth. This order is Saturn, Jupiter, Mars, the Sun, Venus, Mercury, and the Moon. This arrangement also reflects the order of planets from slowest to fastest in the night sky.

Different cultures have developed distinct types of weekday naming systems. In the Greco-Roman tradition, days are named directly after the planets and their corresponding gods. For example, Sunday is the day of the Sun, and Tuesday is the day of Mars. In the Germanic tradition, a process called interpretatio germanica was used. This process involved substituting Roman gods with Germanic deities. This occurred between 100 AD and the 7th century. In this tradition, Thursday became Thor's day, matching the Roman day of Jupiter. Wednesday became Woden's day, matching the Roman day of Mercury.

The history of the week shows how it evolved within the Roman Empire. Between the first and third centuries CE, the Romans replaced an eight-day cycle called the nundinal cycle. The seven-day week became official under Emperor Constantine in AD 321. Before this, eight-day and seven-day weeks existed side-by-side. Constantine also made the Day of the Sun, or Sunday, a legal holiday. Following this official change, the seven-day week spread throughout the Empire. It eventually moved through Christian cultures across the entire world.

The significance of these names is visible in the diverse languages spoken today. Romance languages mostly preserved the Latin names. However, many changed the name of Sunday to mean "the Lord's Day" or Dominica. Most Romance languages kept the Latin-derived names, but Portuguese and Mirandese use numbered weekdays. In these languages, special names like sábado and domingo are kept only for the weekend. Even constructed languages like Esperanto use these ancient roots. Esperanto often draws its names from French to maintain these connections.

There are many notable examples of how regional cultures adapted these names. In Old Irish, the system was complex and included various lists. One list followed the Hebrews, while another followed the "ancient gentiles," or Romans. The Irish also used terms of Norse origin for certain days. In Welsh, the language uses a unique structure for time. Instead of just naming the day, speakers use words for "morning," "night," or "afternoon." This means a person might say "Monday morning" rather than just "Monday."

Today, the way we count the week connects to international standards and local customs. The international standard ISO 8601 treats Monday as the first day of the week. However, many countries still count Monday as the second day. Some cultures still view Sunday as the first day. This is due to its history as the day of the sun god, Sol Invictus. Whether a week starts on Sunday or Monday, the seven-day structure remains a universal way to organize human activity.