12th Night

Bit of a debate in our house about when Twelfth Night actually is - we denuded the flat of decorations this morning (though I may have been tempted to do it yesterday if we had been home in time).

So was a tad bothered this evening to see that B's friend EJ still has her decs adorning her home - eek!
Granted, she had invited us round for a wonderful dinner and I guess wanted the place to still look cosy and festive, but I am worried.

Is there a definitive answer? Does it matter?