Utility to parse Microsoft's JSON dates (JavaScriptSerializer, DataContractJsonSerializer)

ms-json-dates.js

define([
   "underscore"
], function (_) {
   return {
       _msJsonDateFormat: /\/Date\((\d+)(?:([\-+])(\d+))?\)\//i,

       toJSON: function (date) {
           if (!_.isDate(date)) {
               return null;
           }
           var offset = date.getTimezoneOffset() * 60000;
           var utcTime = date.getTime() + offset;
           return "/Date(" + utcTime + ")/";
       },

       parse: function (msJsonDate) {
           var res = this._msJsonDateFormat.exec(msJsonDate);
           if (!res) {
               return null;
           }
           var ts = parseInt(res[1], 10);
           var offset = 0;
           if (!_.isUndefined(res[2]) && !_.isUndefined(res[3])) {
               var east = res[2] == "+", tzoffset = res[3];
               var hh = parseInt(tzoffset.slice(0, 2), 10)
                 , mm = parseInt(tzoffset.slice(2), 10);
               offset = (hh * 60 + mm) - new Date().getTimezoneOffset();
               if (east) offset = -offset;
           }
           return new Date(ts + offset * 60000);
       }
   };
});

you have some bugs here, don't you?