CE and BCE

Every society and culture has had its own ways of measuring time. Big events, such as the birth of an important person or the start of a ruler's reign, often marked the beginning of a new era (a separate period of time).

Today the Gregorian calendar is used all over the world. Alongside it, Hindu, Muslim, Jewish, Chinese and other calendars are still used to work out the dates of festivals and other special days. The Gregorian calendar has not replaced them; it sits beside them.

The Gregorian calendar has 12 months adding up to 365 days, with a leap year every four years. But century years, such as 1800, 1900 and 2000, are leap years only if they can be divided by 400. So of those three, only 2000 was a leap year.

In the West, the traditional year of Jesus Christ's birth was taken as the starting point of this calendar. Years counted forward from it used to be marked AD; today they are called the Common Era, or CE. For example, 1947, when India became independent, can be written 1947 AD (or AD 1947) or 1947 CE.

Years before that starting point are counted backwards. They used to be marked BC (Before Christ) and are now called Before Common Era, or BCE. For example, 560 BCE is roughly the year the Buddha was born.

Now the catch that trips almost everybody: there is no year zero. The year 1 CE comes straight after 1 BCE. Draw a timeline marking every year from 2 BCE to 2 CE and you will see that only 3 years have passed between them.

So to find the number of years between a BCE date and a CE date, add them, then subtract 1: 2 + 2 − 1 = 3. For the Buddha, in the year 2024 CE: 560 + 2024 − 1 = 2,583 years ago.