Just saw this over on the AD blog.

10 years ago, Microsoft’s largest internal domain was upgraded to Windows 2000 becoming the first production Active Directory, and it’s still going strong…

Dn: DC=redmond,DC=corp,DC=microsoft,DC=com
   whenCreated: 4/9/1999 7:49:12 PM Pacific Daylight Time;

redmond.corp.microsoft.com