This command 'rpm -qi fedora-release' gives the following output, which gives the build date of Fedora as the OS on the system:

Name : fedora-release Relocations: (not relocatable)
Version : 5 Vendor: Red Hat, Inc.
Release : 5 Build Date: Tue 14 Mar 2006 11:20:53 PM PDT
Install Date: Fri 02 Feb 2007 11:17:59 PM PDT Build Host: hs20-bc1-6.build.redhat.com
Group : System Environment/Base Source RPM: fedora-release-5-5.src.rpm
Size : 3484422 License: GFDL
Signature : DSA/SHA1, Tue 14 Mar 2006 11:32:36 PM PDT, Key ID b44269d04f2a6fd2
Packager : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>
Summary : Fedora Core release file
Description :
Fedora Core release file

But these commands do not necessarily give out the same release/build related info of a certain package, why so? Thanks......

[root@localhost Desktop]# rpm -qi php-release
package php-release is not installed
[root@localhost Desktop]# rpm -qi mysql-release
package mysql-release is not installed
[root@localhost Desktop]# rpm -qi ruby-release
package ruby-release is not installed
[root@localhost Desktop]# rpm -qi python-release
package python-release is not installed