Yum Package Version

Hi,

I am trying to do determine how yum decides which rpm is the latest version.  For instance, I have created a repo with createrepo command, and have rpm(s) as such,


  *   my-package-2014-05-05-12345-200.rpm
  *   my-package-2014-05-05-12346-200.rpm
  *   my-package-2014-05-05-12347-201.rpm
  *   my-package-2014-05-06-12348-201.rpm

When I ask yum to install my-package, it appears to pick arbitrarily a version.
Does yum expect a particular versioning format?
Is there anyway to specify a versioning format for yum to use?


Sean