All South Koreans have instantly become a year or two younger, as the country ditched its traditional – and increasingly unpopular – system for counting someone’s age and replaced it with the internationally accepted method.

Under the previous system, the country’s citizens are deemed to be a year old when they are born, and a year is added every 1 January. The unusual custom meant that a baby born on New Year’s Eve would become two years old as soon as the clock strikes midnight.

But under the revisions introduced on Wednesday, ages will be calculated in the same way as the rest of the world in most administrative and civil matters, including contracts and other official documents, the Korea Times said.

The national assembly, which approved the change in December, said it would “resolve the social confusion caused by the mixed use of age calculations and the resulting side effects”.

While the global standard has applied to medical and legal documents since the 1960s, other official forms have continued to use the traditional method.

The system has attracted criticism in recent years from politicians who argue that it causes confusion and makes South Korea, a global technological and cultural power, appear out of step with the rest of the world.

The president, Yoon Suk Yeol, said the existing arrangements were a drain on the country’s resources. In