Date.prototype.DateAdd = function(strInterval, Number) {      var dtTmp = this;      switch (strInterval) {          case ‘s‘ :return new Date(Date.parse(dtTmp) + (1000 * Number));          case ‘n‘ :return new Date(Date.parse(dtTmp) + (60000 * Number));          case ‘h‘ :return new Date(Date.parse(dtTmp) + (3600000 * Number));          case ‘d‘ :return new Date(Date.parse(dtTmp) + (86400000 * Number));          case ‘w‘ :return new Date(Date.parse(dtTmp) + ((86400000 * 7) * Number));          case ‘q‘ :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number*3, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());          case ‘m‘ :return new Date(dtTmp.getFullYear(), (dtTmp.getMonth()) + Number, dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());          case ‘y‘ :return new Date((dtTmp.getFullYear() + Number), dtTmp.getMonth(), dtTmp.getDate(), dtTmp.getHours(), dtTmp.getMinutes(), dtTmp.getSeconds());      }  };