Excel IF statements

Hi, having a problem with IF statements and dates

In column “D2” I have a date say 21/10/11, in column “E2” I want to return the words “Working After 24th Dec 2011 else “Left before 24th December 2011”.
I wrote the following IF statement
=IF(D2>=24/12/2011,"Working After 24th Dec 2011","Leaving Before 24th Dec 2011")

But all columns say “Working After 24th Dec 2011” even those that have an end date before 24th Dec. What have I done wrong? What should the statement be?

Thanks in advance for your help. Lisa