Question: is there a plugin or some configuration in Hudson CI where the job will not run during a certain time of day? I was thinking of a job like:

Run job A on version control change if not after 5pm and before 9am

Thanks!

Answer: 
Maybe you could set up a global property that gets set to on/off depending on time and you configure the builds to use that global property.

But the best way would probably to set up the scm polling to just not poll at the desired time of day. Then no changes are found and no build is triggered ;-)
We run automated tests in our Jenkins instance. When these are being run on certain environments, we disable the deploy job to the involved environments. This is done using Jenkins CLI. <https://wiki.jenkins-ci.org/display/JENKINS/Jenkins+CLI>
I bet you could do the same thing but instead use the "Build periodically" function in the job.