This morning Windows Update informed me of the availability of KB3217877, as well as KB4012864. Both have a Windows Update publication date of March 21. The latter KB is for DST changes in Windows for Northern Cypress, Mongolia, and Russian Saratov region.
KB4012864 is a checked important update, KB3217877 is an unchecked optional update. A Google search gives no results for KB3217877. I can find it in the Microsoft Update Catalog though, only available for Windows Vista and Server 2008, but with March 16 as the date.
Any ideas about what KB3217877 is?
I am running Vista BTW.