Interesting; this is what TD WATERHOUSE in Canada has on their website for Canadians:
Final trading dates for 2011 settlements
If you wish to sell a publicly traded stock to realize a capital gain or loss in 2011, please note the following final trade dates for orders to settle in 2011:
* Canadian Equities: 4:00 p.m. ET on Friday, December 23, 2011
* U.S. Equities: 4:00 p.m. ET on Tuesday, December 27, 2011