Question

If the Google Code Prettifier (or JQuery Syntax Highlighter) is being used in the same page as the JQuery DatePicker, neither will work properly. Why is this?

Answer 1

Because they both monkey patch a now method onto the native Date object!

Prettify does this:

var clock = Date;
if (!clock['now']) {
  clock = { 'now': function () { return +(new Date); } };
}

DatePicker does this:

Date.now=function(){return new Date();}

So Prettify’s returns an int representation of the Date (so that it can add on some ms) while DatePicker returns a Date.

(IMO this kind of thing is outrageous in two such commonly-used libraries.)