The other day I was wondering where the AssemblyVersion build and revision numbers come from if you use the default synax in your AssemblyInfo files:

// Version information for an assembly consists of the following four values:
// Major Version
// Minor Version
// Revision
// Build Number
// You can specify all the value or you can default the Revision and Build Numbers
// by using the '*' as shown below:

[assembly: AssemblyVersion("1.0.*")]

Well it turns out that the build number is set to the number of days since a
random, designated start date, and the revision based on the number of
seconds since midnight.

It's interesting that it took 15 or so minutes on google to find this post that has this little nugget.