Its mother, the continent, gave birth somewhere between 450000 and 150000 BC.
The exact date has been forgotten.
It collided with Scotland about 490 million years back. We're still sorting out the insurance.
Actually, I was in a discussion only today about when England (Engla-lond) was first so-named,
the answer is, as RR's suggested, late 9th century, the time of Alfred.
But the concept of 'England' was only just taking shape then -
Alfred was only ever titled King of the West Saxons.
His grandson Athelstan had received homage from the rulers of the Danes of York
the Cumbrians of Cumbria/ Strathclyde, and the Scots,
but he was titled King of the English 927-939 -
early kingdoms were more usually of peoples rather than of lands
(we had Kings of Scots - and Mary Queen of Scots - right up to the Union of the Crowns),
Eadgar was the first to actually be called King of England, 959-975.