Actually Chanukah DID happen on the date the Jewish calendar claims it did. The Eight day Chanukah festival begins on the twenty-fifth of the Jewish month of Kislev, every year. When that corresponds to the Gregorian calendar changes from year to year but it's celebrated on the correct date of the historical occurance.
Which is more than can be said for Christmas.
....the twenty-fifth of the Jewish month of Kislev, every year......that 25th is always Christmas!
Merry Christmas
(Support your local 'Manger' builders!)
Merry,....Merry Christmas,......is a 'sign'......a Manger Sign...!