Where did the division of the week into 7 days come from? Most people would point out the Bible and the process of creating the world written there. However, it is not so certain that the Hebrews were the creators of the 7-day week used to this day.
The Babylonians had already discovered the existence of planets and, as the Greeks later, were able to name seven of them (including the sun and moon). Each of these celestial bodies corresponded with one of the days, so we had the day of Saturn, the day of the Sun, the day of Mars, etc. This division functioned in the days of the Roman Republic and was later officially approved by Emperor Constantine.
The echoes of ancient beliefs are still visible in many languages today. The Day of the Sun is a well-known Sunday – Sunday (English) or Sonntag (German). In turn, Monday is the Day of the Moon (Latin luna) in French known as Lundi, in Italian as Lunedi, and in Spanish as Lunes. Tuesday is Mars Day (French Mardi, Spanish Martes, Italian Martedi). Wednesday is the day of Mercury (Mercurii dies) – Mercredi in France, Mercoledi in Italy, Miércoles in Spain. Thursday was the festival of Jupiter (French Juedi, Spanish Jueves, Italian Giovedi), and Friday was Venus (French Vendredi, Italian Venerdi). Saturday was celebrated as the festival of Saturn (called Saturday). In Germanic languages there was also a place for the local gods: Thora (Thursday) or Donar (German Donnarstag), who could be equivalents of the Roman Jupiter.