It is: TODAY
eighteen August two thousand eleven
Providing that is the current date; Today
You cannot do it (Answer dated: 27 Aug 2011).
To write 24 January 2014 in 5 letters without using numbers kindly write 24.1.14.
As long as you read this on 16 August 2011: "Today" If you read this on 17 August 2011, you'll need nine letters: "Yesterday" If you read this before 23 August 2011, you'll need 11 letters and 1 space: "Last Tuesday" Beyond that I give up.