24 years, to the day. 1 July 1987 to 30 June 2011.
At the age of 61, I have retired from my 'government job' with 24 years of service, however, I had purchased two years of prior (military) service so I am credited on the books with 26 years toward my retirement. This pushed me over the 25 year marker and has made a significant difference in my benefits.