Counting the days of the year

On Sunday, a new year will begin – at least according to one of our two main calendars

As the world celebrates the change from 2016 to 2017, it’s worth remembering that it is still the year 1438 in the Islamic tradition, and next year will be 2560 in Thailand and it will be the year 4715 in China from January 28. Louise Wateridge / Getty ImagesShow less

As the world celebrates the change from 2016 to 2017, it’s worth remembering that it is still the year 1438 in the Islamic tradition, and next year will be 2560 in Thailand and it will be the year 4715 in China from January 28.

In a globalised world, we have standardised time and the days of week. And yet many parts of the world use a different calendar, meaning we disagree on which month it is and even which year.

The Gregorian calendar, the calendar most widely used today, was named after Pope Gregory XIII, who introduced it after a proposal from the Catholic Church in 1582. The first eight months are named after various gods, goddesses, festivals and rulers. For instance, January was named after Janus, the Roman god of doorways and beginnings and February was named after Februa, a feast of purification.

However, September and October literally mean “seventh month” and “eighth month”, followed in the same manner by November and December, since the original Roman calendar had only 10 months.

Although the Gregorian calendar had become the official calendar used for international events and business, there are other regular calendars still in use, including of course the Islamic calendar, the Chinese calendar, the Hebrew calendar, the Persian calendar, the Ethiopian calendar and several others.

Such diversity naturally follows the various gyrations of the solar system, which made it impossible to come up with a one-size-fits-all calendar that can be used in all parts of the world reliably. Most calendars use what are called “intercalary” days – or even months – that go in line with the tropical year, which is the time taken by the Earth to make one revolution around the Sun. In the Gregorian calendar, this is the leap year day tacked on to the end of February.

While the Gregorian calendar is a solar calendar, lunar calendars – such as the Islamic calendar – are based on cycles of phases of the Moon. Some of them have 13 months and some others require a 13th month to be added every few years – a leap month.

Even the start of a day can differ. Nowadays, global standards of time calculations are pretty strictly controlled, marking a new day at midnight. But for thousands of years, astronomers counted a day from noon to noon.

Different cultures had their own benchmarks. Hindus and Egyptians marked a new day at dawn, but Babylonians, Greeks, Jews and Muslims started at sunset. Many people still use these milestones to mark the beginning of religious or cultural events.

Without a calendar, we wouldn’t know what day it is, we would forget birthdays, anniversaries, and miss appointments. We also wouldn’t have the opportunity to make New Year’s resolutions. But it’s worth remembering that the rest of the world isn’t always in step with us: after all, by the time you start your latest New Year’s resolution, someone else may already have broken theirs.