I have a controller action that effectively simply returns a JsonResult of my model. So, in my method I have something like the following:
return new JsonRes
Here's my solution in Javascript - very much like JPot's, but shorter (and possibly a tiny bit faster):
value = new Date(parseInt(value.substr(6)));
"value.substr(6)" takes out the "/Date(" part, and the parseInt function ignores the non-number characters that occur at the end.
EDIT: I have intentionally left out the radix (the 2nd argument to parseInt); see my comment below. Also, please note that ISO-8601 dates are preferred over this old format -- so this format generally shouldn't be used for new development. See the excellent Json.NET library for a great alternative that serializes dates using the ISO-8601 format.
For ISO-8601 formatted JSON dates, just pass the string into the Date constructor:
var date = new Date(jsonDate); //no ugly parsing needed; full timezone support