Clok is a new way to view time. For many of us 'what time is it?' is less important of a question than 'when is it?' The distinction is subtle but important. What time is it? is usually answered with a quantitative value, say, '3:16pm'. Unfortunately we are much better at evaluating spatial or graphic relationships than we are at numeric ones. Thus clok tries to represent the time graphically without reference to a specific time.
Note that clok does not replace a real clock. In fact, I run it simultaneously with xclock so I can know what time it is. What it does help me do is understand what time it is in Australia where some of my co-workers are. This visual understanding is something that all the metal timezone math will never do.
To run it, invoke the jar with no command line parameters for a list of time zones your Java runtime knows about, and then re-run with a list of zones you wish to have displayed. The time is updated about once a minute. You can add a specifier of human, server or hacker to tweak the boundaries that are used to delineate the areas of dark versus lighter color.
This is better explained at the distribution site.
Here's the command I use:
$ java -jar clok.jar "America/Los_Angeles" "Australia/Brisbane:human"
For the PHP version (introduced in 1.2) you need to have PHP 4.0.6+ and GD 2.0.1+. I don't know much about PHP but from what I'm told, all you need to do is make the clok.php accessible and link to it according to the information provided in the header.
The Clok distribution site is http://www.technocage.com/~caskey/clok/ Clok was originally written by Caskey L. Dickson <caskey@technocage.com> Clok/PHP was written by Steve Babineau <iam@nkrm.org>