docs: function dateParser(clockSkew) {
  
      var normalizedClockSkew = clockSkew || 300;
      assert.number(normalizedClockSkew, 'normalizedClockSkew');
  
      normalizedClockSkew = normalizedClockSkew * 1000;
  
      function parseDate(req, res, next) {
          if (!req.headers.date) {
              return (next());
          }
  
          var e;
          var date = req.headers.date;
          var log = req.log;
  
          try {
              var now = Date.now();
              var sent = new Date(date).getTime();
  
              if (log.trace()) {
                  log.trace({
                      allowedSkew: normalizedClockSkew,
                      now: now,
                      sent: sent
                  }, 'Checking clock skew');
              }
  
              if ((now - sent) > normalizedClockSkew) {
                  e = new RequestExpiredError(OLD_MSG, date);
                  return (next(e));
              }
  
  
          } catch (err) {
              log.trace({
                  err: err
              }, 'Bad Date header: %s', date);
  
              e = new InvalidHeaderError(BAD_MSG, date);
              return (next(e));
          }
  
          return (next());
      }
  
      return (parseDate);
  }