The 186,000 residents of the island of Samoa will go to bed on December 29th and wake up on December 31st. They will have missed a whole day!
No, they won't have slept 24 hours, they will simply be experiencing the legal shift of their country from one side of the International Dateline to the other. A law passed by the Samoan government will move Samoa west of the International Dateline. Due to this change, Samoa will be skipping December 30th this year.
Up until now, Samoa was one day behind their international trading partners in Australia and New Zealand. Consequently if something had to be urgently taken care of with a New Zealand company on Monday morning, Samoans had to get to the office Sunday morning to take care of it. It also meant that there were only 4 days a week where they could do business with their closest business neighbors which include New Zealand, Australia, China and Singapore.
Some Samoans are upset with the fact that their country now loses the notoriety of being the last country to see the sunset, however, most business people are pleased with the change.
So if your birthday or wedding anniversary is on December 30th, this year in Samoa you won't get the chance to celebrate it. Though of course, you could take a one hour flight to American Samoa and there you will find a December 30th in full swing. The American island is remaining on the side of the line that is closest to the United States.
Read more about this change at The Guardian.