code: function (offset) {
                  if (undefined === offset) {
                      offset = this.offset;
                  }
  
                  // new Date(1970, 1, 1).getTime() - new Date(1904, 1, 1).getTime();
                  var delta = -2077545600000;
                  var time = this.readUint32(offset + 4, false);
                  var date = new Date();
                  date.setTime(time * 1000 + delta);
                  return date;
              }
docs: 读取长日期
  
  @param {number} offset 偏移
  @return {Date} Date对象