People living in South Korea awoke on Wednesday morning to find themselves a year or two younger, at least on paper.

As reported by CNN, the change is due to the country adopting the “international age” system used by a majority of the world, and moving away from the formerly used “Korean age” or “calendar age” systems.

The “international age” system starts at zero and refers to the number of years since a person was born, while the “Korean age” system considers a baby as a year old on the day they’re born.

Meanwhile, “calendar age” takes elements from both systems, and considers newborn babies as zero years old, then adds a year to their age on January 1st of each year.

Although the commonly used “international age” system will now be standard, the old systems will still be used in certain situations.