Formerly, Samoa’s calendar was aligned with eastern neighbors, the most influential of which is the U.S.
Today — or rather Saturday — Samoa’s calendar is aligned with western neighbors of Australia, Japan, China and Russia.
Samoa’s closest neighbor, only about 100 miles to the east, is the unincorporated U.S. territory of American Samoa, which did not change its calendar.
Samoa’s decision to adjust its calendar will require map makers to redraw maps that show the international date line — the geopolitical line where today becomes tomorrow.
The time zone capital of the world is Greenwich, England — which, by long standing international agreement, is situated on the prime meridian at zero degrees longitude.
Grand Haven’s longitude is 86.22 degrees west (of Greenwich, England) and 43.06 degrees north (of Earth’s equator).
And Grand Haven is on the far western edge of the U.S. Eastern time zone, which (when we are not in daylight time) puts our clocks five hours behind clocks in Greenwich, England.
The U.S. Eastern time zone is UTC-5, which is short for Coordinated Universal Time minus five hours.
Samoa’s longitude is 171.83 degrees west and 13.83 degrees south — almost exactly on the opposite side of the world as Greenwich.
Samoans, then — and everyone living near 180 degrees longitude — have a choice to make: Shall they reckon their home is halfway around the world from Greenwich to the west or to the east? If they reckon they are west of the prime meridian, as Samoans did until yesterday, then their time and date follow Greenwich by 12 hours. If they reckon they are east of Greenwich, as they do now, then their time and date lead Greenwich by 12 hours.
One calendar day becomes the next at midnight local time. This happens after it does in Greenwich for locations to the west, but before it does in Greenwich for locations to the east.
Suppose it is noon on a Thursday in Greenwich. For locations west of Greenwich, all the way around westward to the international date line it is earlier in the day on Thursday; for locations east of Greenwich, all the way around eastward to the IDL it is later in the day on Thursday.
But when clocks in Greenwich tick to 12:01 p.m., it becomes Friday just west of the IDL, while it is still Thursday just east of the IDL.
A traveler making even the shortest trip eastward across the IDL must subtract 24 hours — a full day — from his or her clock/calendar, and so must live again through the same calendar day. But a traveler making even the shortest trip westward across the IDL must add a full day to his or her calendar, and thus completely skips a day.
By deciding to align their calendar with countries to their west, Samoans have in effect moved their island nation westward across the IDL, and they have skipped a day.
Samoans decided to skip Friday, Dec. 30, 2011 (today). Thursday, Dec. 29, ticked directly to Saturday, Dec. 31 — and now in Samoa, it is already New Year’s Eve.
The most generous aspect of Samoa’s calendar adjustment, however, is that the government stipulated that all workers shall be paid for working the Friday that never came to pass.
— By Doug Furton, a member of the physics faculty at GVSU. Send questions and suggestions to firstname.lastname@example.org.