The International Date Line was created in 1880 and gave the starting and finishing point for time zones. Those countries bordering the line that runs through the Pacific can opt whether to be on the east or west side and the line will be changed to accommodate this.
Samoa has decided that later this year it will align itself more with Australia and New Zealand. Consequently it will switch to being three hours ahead of Sydney rather than 21 hours behind it. The day selected is Thursday 29 December and, if you have a birthday on that day while in the island-nation, it will be difficult to celebrate. The day will just disappear.
In 1892 Samoa had turned the other way, towards San Francisco which they considered to be a more important trading contact. This was achieved by having one day repeated and that was, Monday 4 July, American Independence Day. This was something of a challenge for visiting Americans who had to party for 48 hours.
Scottish islands do seem to have a different time zone - especially in the months of May and June when night-time recedes to just a few brief hours.
Scottish Islands Explorer - appears one day in every 56