Hold the celebrations for the dawn of a new decade. Put a pause on the spectacle and ease the pressure on your decade-long resolutions — the new decade may not even have started.

In recent years there has been a debate about when a decade begins: in a year ending in a zero, or a year ending in a one. 

While popular culture celebrated the start of a new decade in 2020, scientific convention differs in its definition of the start of a decade.

In 1999, Geoff Chester, an astronomer and public affairs officer at the United States Naval Observatory, which runs the master clock for the United States, said that the new millennium began on Jan. 1, 2001. His reasoning behind this is that the observatory uses a modification of the Julian date to measure time, which is used by astronomers and geodesists, with the original Julian date beginning at 4713 B.C.

In addition to the Julian date, in 525 monk Dionysius Exiguus, while trying to determine a date for Easter, created a calendar called anno Domini, which translates to “in the year of our Lord” and is where the abbreviation A.D. originates, according to the New York Times. The calendar was based on when he believed Jesus was born—yet, as the concept of the number zero as used today did not exist in Europe until the 13th century, the calendar assigned the year of Jesus’ birth to Year 1, not Year 0, according to timeanddate.com.

Because of this gap, one full year had passed between the end of Year 1 A.D. and the end of Year 1 B.C., instead of the two which would have passed if Year 0 had existed. 

This concept can be compared to the way that Americans calculate our ages. We are born at the age of zero and each year we gain a year; however, if we determined how old we are based on the same system of anno Domini, we would be born at age one, thereby adding a year to our current age without us aging.

The definition of when a decade begins is not governed by legal guidelines, according to the New York Times, so there are two interpretations of whether or not a new decade has officially begun, Mordecai-Mark Mac Low, a curator in the department of astrophysics at American Museum of Natural History, said to the New York Times: the new decade begins in 2021 based on the modified Julian date or the decade already started in 2020 as accepted by popular usage. 

While the new decade may not have started according to scientific convention, popular culture has assured that it has — so might as well celebrate the start of the decade twice.

Overall, the beginning of the new decade is only based on the Gregorian calendar, while other calendars such as the Jewish, Islamic and Hindu calendars have completely different year numbers, so, from a certain perspective, the earth has rotated around the sun well beyond 2020 times, with each new year simply the start of another turn around the sun.