Extract date from string in T-SQL

Hi,

I am having one field(AT_TEXT) in my database that has below kind of values. I want to extract date from this string but the issue is all rows has different format.

1)One Month Lttr sent on 3/12/2009 due to

2)One Month Letter sent on 1/15/2009 due to

3)One Month letter sent on7/15/2011.The amount due             - This has no space between on and 7 and . after yr

4)One Month letter sent on 7/16/12 due to        - This has 12 instead of 2012(2 positions after 2nd slash/)

Can anyone please help me to write query to extract date from this string?

Vicky