Parse both dates with Date.js, it will understand both formats and then you can compare them.
After importing the library you can use
date1 = Date.parse(Fri Oct 19 2012 13:35:45 GMT+0200);
date2 = Date.parse(2012-10-19 12:14:13); // or whatever date
isGreater = date1.isAfter(date2);
As gdoron stated, you don't need date.js, but it may be worth taking a look, especially if you are likely to manage weird looking date formats or make tricky operations.