There are basically two types of JavaScript countdown scripts, depending on what you're trying to do. The first type counts down using the time of the visitor's computer, which obviously varies depending on the visitor, and is great for counting down to "relative" events such as Christmas, your friend's birthday etc. The second type counts down using a specific local time (ie: Time in New York), and is great for counting down to "absolute" events where the target date/time is tied to a certain time zone, such as the launch date of a web site, the date/time of the next Solar Eclipse etc