On this date in 1967 the Principality of Sealand was founded, or the land was first occupied or the permanent residency of its future ruler began or however you want to characterize it. Their official website has been inaccessible since at least last night, but the history page reports that part of the micro-nation's history:
After WWII ended, the troops were withdrawn from all bases by the British Admiralty. None of them was ever used by the United Kingdom again, leaving the forts deserted and abandoned. Except for the aforementioned fortress, the bases were subsequently pulled down. This resulted in the portentous uniqueness of the fortress. Fort Roughs Tower, situated at the high seas, had been deserted and abandoned, res derelicta and terra nullius. From a legal point of view, it therefore constituted extra-national territory.
The Birth of Sealand
This paved the way for occupation. On 2 September 1967, former English major Paddy Roy Bates formally occupied the island and settled there with his family. After intensive discussions with skillful English lawyers, Roy Bates proclaimed the island his own state. Claiming jus gentium, he bestowed upon himself the title of Prince and the title of Princess to his wife and subsequently made the state the Principality of Sealand. Roy Bates, henceforth Roy of Sealand, exerted state authority on the island and thus was an absolute sovereign. The royal family and other persons that have declared loyalty to Sealand have occupied Sealand ever since.
About.com's Geography page claims The Principality of Sealand does not qualify as a legitimate country, saying,
but what fun is that!The Principality of Sealand fails on six of eight requirements to be considered an independent country and on the other two requirements, they're qualified affirmatives. Therefore, I think we can safely say that the Principality of Sealand is no more a country than my own backyard.