Hey I need to set up a countdown on my website that count's backward to the next 0,20 or 40 min of each hour.
I mean that if the time for example is 08:14:20 it will print that there is 5 min and 40 sec left.
if the time is 11:37:05 then it'll print 2 min and 55 sec.

I dont want to do it by only counting down from 20 each time, because I need it to bt set up with the server time perfectly.

I'm not asking you to make it for me. only for and idea of how to make it.

Thank you!