JowClock is a clean and simple but very functional clock module for Joomla. Unlike most Joomla clocks I could find this does not use Javascript to get the time but instead does so through PHP which means mainly two things.

1. Everyone visiting the page will get the same time even if the clock on their computer is wrong as it uses the Server clock.
2. It has access to the handy timezone options in PHP, e.g "Europe/London" and "America/New_York".
3. Tons of options

The only drawback that I know of myself is that since the only time it actually gets the time is when the page loads and then keeps it ticking with Javascript, this means the clock might fall behind a few seconds if the browser were to lock up or be otherwise sluggish for a moment or, worse, mobile browsers where Javascript is suspended when you hold your finger on the screen or minimize the browser.
However, JowClock will notice if any time has been missed due to any form of Javascript slowdowns and correct for this.

JowClock version 1.0 is a fork of leoClock .  I wanted extra features and RWD design.