Astronomical events, such as a solar eclipse, are relatively rare. Having a countdown to such an event helps to build up the anticipation.
This sample countdown clock has a few predefined astronomical events that can be used to prefill the form with one click.
You can find more dates of solar and lunar eclipses and other astronomical events, such as Mercury transitions, at NASA's Eclipse Home Page.
Just edit the title to be whatever you would like it to be and click on the Generate Pop-up Code or Generate iFrame Code button.
There are many browsers and platforms, things do not work the same way for all. I have done my best to make it as compatible as possible but if you still find problems or errors please report them to me: E-mail Otto de Voogd