Countdown from server time

Hi!

I am trying to find a way to setup a timer that will count down in 30 minute blocks, and once it reaches 0 reset to 30 minutes and count down again.

But, i want this to be based on the web servers time, so that the 30 minute blocks are based on the clock on the server, and represent exact parts of the current hour.

Any ideas? (Also, the site is built in ASP)…