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How Can Samoa Hop Over the International Date Line?

A bill written by the Prime Minister of Samoa's Cabinet and approved by its Parliament will soon send Samoa to the other side of the International Date Line, an imaginary line that defines when one calendar day begins and the other ends.

The change, to take effect on December 29, won't shift the time of day in Samoa -- after all, the sun will still rise and set as it did before; instead it will move the calendar one day forward. Next year, 12 pm on a Tuesday in Samoa (west of the date line) will be 12 pm on Monday in American Samoa, an island 80 miles to the east that plans to remain east of the date line.

The International Date Line runs roughly along 180 degrees longitude through the middle of the Pacific Ocean . The line is defined by practice rather than any international body; its zigzagging route is decided upon by the governments of the countries that lie near it. Each country has the freedom to choose which side of the line it falls on, depending on what would be more convenient.

Samoa used to fall west of the line -- where it will soon fall again -- but moved east on July 4, 1892 in order to improve trade with the United States and Europe. Today, it trades more with its closer neighbors, Australia, New Zealand and Asia, which all fall west of the International Date Line, and thus would benefit from sharing its weekends with them.

"There is no feasible reason why we should continue with the current time situation," Samoan Prime Minister Tuilaepa Sailele Malielegaoi told reporters. "Things will be much easier, much more convenient if we move back to sharing the same time zone with Australasia."

As well as being good for trade, Tuilaepa said he hopes the move will be good for tourism as well. "If we move the dateline to between here and American Samoa, you can travel between two time zones in less than an hour. So you can have two birthdays, two weddings and two wedding anniversaries on the same date -- on separate days -- in less than an hour's flight across, without leaving the Samoan chain.

"We are looking forward to working with American Samoa on capitalizing on the sort of tourism this change could generate."

Some Samoans involved in the tourism industry are unhappy with the upcoming change. "The fact that Samoa is the last place on Earth to see the sun of every day is a great marketing point," tour guide Andrew Tiatia told the New Zealand Herald, "and one which I take great pride in telling our visitors. Once that's gone, we're just like the rest of the world."

Follow Natalie Wolchover on Twitter @nattyover.

Natalie Wolchover
Natalie Wolchover

Natalie Wolchover was a staff writer for Live Science from 2010 to 2012 and is currently a senior physics writer and editor for Quanta Magazine. She holds a bachelor's degree in physics from Tufts University and has studied physics at the University of California, Berkeley. Along with the staff of Quanta, Wolchover won the 2022 Pulitzer Prize for explanatory writing for her work on the building of the James Webb Space Telescope. Her work has also appeared in the The Best American Science and Nature Writing and The Best Writing on Mathematics, Nature, The New Yorker and Popular Science. She was the 2016 winner of the  Evert Clark/Seth Payne Award, an annual prize for young science journalists, as well as the winner of the 2017 Science Communication Award for the American Institute of Physics.