This time is needed to rebuild, validate, test (QA), translate and integrate new artwork.
Please see The Cent OS Rebuild and Release Process for further details.
If Cent OS is important to you, please support the long-term viability of the Cent OS project.
sha256sum information via an https source is provided in the Release Email or Release Notes link above.
The Cent OS team recommends that you start moving workloads from Cent OS Linux 6 to Cent OS Linux 7.
It is recommended that you plan to upgrade before this point whenever possible.
New major and minor releases are available about 2 to 6 weeks after upstream (Red Hat) publishes the SRPMs (source packages) of their product.
You can also use the sha256asc file located in any Cent OS directory with ISO or Cloud images.
You should always verify your downloads before using.
Once a new point release is issued (say: 6.3, following 6.2), no further source packages (from which updates can be built) are released for the earlier version and therefore Cent OS is no longer able to produce security or other updates.