Squid can be configured to deploy restrictions based on day/time parameters (nothing directly related to bandwidth). Squid has some bandwidth handling facility (if compiled with it). Once I stumbled upon this artice on delay pools
of Squid. This is another I found named Reining in Bandwidth With Squid Proxying
. But using Squid for total bandwidth management is not goog enough I think. As far as I got, I believe Squid solution would only provide management of it's own (HTTP) traffic only. I'll post some other links wich might be useful to you.
is a traffic shaping software. Here's a link to a Linux traffic shaping
article. Although not relevent to your task directly, if you have time have a look at WonderShaper