I have heard the question about creating rules that execute only during a certain set of hours many times in the last while. While its not straight forward, it is still possible. Attached to the this blog post is a MHTML file which I wrote that describes the steps of how this can be done and also gives you some clues as to how this can be done for a monitor. The MHTML file includes step by step instructions on how this can be done and also provides screen shots. The first time you do it, it will probably take 10-15 minutes. However the next time you do it, I think it will be pretty quick.
If you have questions about the steps written in the MHTML file, please leave me a comment. If you find this useful, please also leave me a comment and I can put together a sample for a monitor.