For me ... it has always been Twelfth Night or January 6th ... the beginning of Epiphany ....
[B]The following is from Wikipedia. Where it says:
January 6th is Three Kings Day. It is the beginning of Epiphany -- The celebration of the Jesus public appearance in the world. So Christmas is over.
So Jan 6th is the end of the celebration of Christmas and so the decorations go down. Christmas starts several (4) weeks before the 25 with the lighting of the candles in the Advent wreath.
So there we have it my friends: While some people take their tree and decorations down early for aesthetics or convenience, the Official Date is the 6th of January and the day of the Epiphany! (The twelfth Day of Christmas!)