the joy of parenting in a world of 24x7 on internet. they could quickly get around this proxy by retrieving the content via another proxy. there are plenty of those on the internet, quite happy to forward entire websites. they could also get another web browser or just change/remove current proxy setting. there's no way to specify a proxy system wide, it's set at application level. also whilst i've setup several squids myself without too much hassle, depending on your confidence and time available to read the details, you may want to avoid that.
what i think you actually want is some good parental controls software that is not visible to the user. there's plenty of that around, and they do have time based url restrictions and various other flexibilities. they hook into the tcp/ip stack, so all traffic is checked against specified rules. a special key sequence and assigned admin password brings up the gui to manage it. they also optionally log all traffic, so you can tighten the rules if needed.
but even these can be thwarted by an enterprising youngster, once they find out they're being watched & ruled 24x7 on internet by parents. hence the only real way is to properly monitor usage as a parent (physical visits to computer room) and early education about time management and the various dangers on the net. being careful not to be too negative/confrontational is key to such dialogue with kids.
the hardest line to type correctly is: stty erase ^H

In reply to Re: local proxy for time based URL blocking by aquarium
in thread local proxy for time based URL blocking by LanX

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.