Some dates of the first time the KGS ranks were reached:
19k - 10/03/08
18k - 15/03/08
17k - 23/03/08
16k - 29/03/08
15k - 08/04/08
14k - 21/04/08
13k - 05/05/08
12k - 10/05/08
11k - 01/06/08