The Longest Year
It's still 1998 in the London Borough of Newham. The reason for this rather odd fact stems from the calendar reforms of 1752; as part of a political compromise to adopt the Gregorian calendar, the burghers of Newham were given the right to ratify every new year's calendar before it came into force.
This ratification proceeded like clockwork for more than 200 years, with the new calendars passing into local law on the nod. However, the debate over the endorsement of 1999's calendar proved to be unexpectedly contentious as the affair became entangled with a dispute over the funding of the Millennium celebrations. The ensuing deadlock has yet to be broken, although a meeting scheduled for December the 2027th 1998 may provide a breakthrough.