In .net, each assembly has a version number, in 4 parts - <major version>.<minor version>.<build number>.<revision> .
The Major Version and Minor Version are always user specified, but you can tell the compiler to generate the Build Number and Revision. People often complain that these numbers don't increment, but instead seem to be based on the system date and time. Which indeed they are.

It turns out that a little playing with a calculator will tell you that these numbers are calculated as follows:
<build number> = number of days since 1 January 2000.
<revision> = number of seconds since midnight / 2 + 60.

I've written a simple converter, where you can paste in your .net version number, and get the date and time that it corresponds to.