Traditionally, Christmas trees are not erected until Christmas Eve (December 24) and then removed after 12 nights (January 6). Advance and postpone this date is considered unlucky. But the modern Christmas shopping season has made most shops set up for Christmas at the end of October. The Christmas department in Selfridge, UK, started business in early September, including the Christmas tree.
Most American families have the habit of putting up Christmas trees immediately after the Thanksgiving Day (fourth Thursday of November) until after the new year. Some American families until December the second weeks set out to erect a Christmas tree, the Christmas tree stood until January 6 (Epiphany).
In Germany, the Christmas tree was traditionally erected on December 24, but it was set up 1-2 weeks earlier.
In Australia, the Christmas tree is just one weeks before the summer vacation, but South Australia is the exception, where most people have set up after the Adelaide Credit Union Christmas celebration in early November.