Most of the ways we measure time are based on nature. The month is broadly based on lunar cycles, with a few days added (by Julius Caesar) to make 12 months fit snugly in a solar year – based, of course, on the time it takes the earth to orbit the sun. Before Caesar revamped it all, months were totally based on lunar cycles, so December crept gradually from winter to summer, which was presumably inconvenient.
But the seven day week? What’s that all about? In ancient times they divided lunar months up all sorts of ways instead. But the Babylonians started dividing the month into seven day chunks, as of course did the Jews.
Witold Rybezynski, in his fascinating book Waiting for the Weekend, points out that the ancient world was full of sevens – seven pillars of wisdom, seven names of God, seven wonders of the world – you name it. Seven was a magical number. There were also thought to be seven planets, and the days of the week were named after the known planets by the Romans: Saturn-day, Sunday, Moon-day, Mars-day (think of the French Mardi), Mercury-day (French Mercredi), Jupiter-day (Jeudi) and Venus-day (Vendredi). In English, we traded some of this for names of Anglo Saxon figures: for example Thor got Thursday. The only European language that retains a complete set of Roman planetary names is Welsh.
In China, though, the seven-day week arrived very much later – as a result of the 1911 revolution, and as part of a push to ‘modernise’.
According to the same book, the ancient concept of the weekend started with the Jewish Sabbath. Then other religions (Christianity, Islam) deliberately chose other days as their holy day to distinguish themselves. Hindus on the Indian sub continent also adopted a rest-day in each seven day time-chunk, probably around the 4th century. There has never been a human society that did not recognise the need for a regular day off, although some have tried to minimise them. One of these was revolutionary France.
After the revolution, the French revised the calendar completely, to break with the past and to decimalise (‘rationalise’) time. Year 1 was to be the proclamation of the Republic, 1792. They kept the year, and divided it into twelve thirty day months, with five days left over at the end for a festival. The seven day week was abandoned – instead months were divided into three ten-day periods, decades, with the tenth day being a holiday. It didn’t work though. Christians (the majority) continued to celebrate the Lords Day, and non-Christians had far less frequent days off. According to Rybezynski, “even if the Jacobins had survived, it is unlikely that the “decade” would have persisted”. It lacked the cultural roots and mystery of the planetary week. “The roots of the week lie deep, too deep to understand.”