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All programming languages have functions.
Functions, or subroutines, as they're sometimes called, are bits of JavaScript that you can call over and over without having to rewrite them every time. The important thing to notice is that it's fairly long. If you wanted to have 10 of these time links, you'd have to cut and paste this script each time, making your HTML pretty long and ugly. In addition, if you wanted to change the script, you'd have to change it in 10 different places. Instead of having 10 copies of it on your page, you could write a function to execute the JavaScript.