Mathematicians and economists at the John Hopkins University in Baltimore have designed a new, leap-year-free calendar.
It means that birthdays, holidays and Christmas would fall on the same day every year.
It is different from the Gregorian calendar, also known as the Christian calendar, that is used by the western world.
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The Gregorian calendar - a reform of the old Julian calendar was first introduced by Pope Gregory XIII in 1582.
In the leap-year-free calendar, each year would be 364 days long, and every five or six years there would be a week-long 'mini-month' to keep the calendar in tune with the solar cycle, instead of using leap years.