docs: function validTimestamp(timestamp) {
      // ^year-month-day(Thour:min:secms?timezone)?$
      var year = /((?:[1-9][0-9]*)?[0-9]{4})/,
          month = /(1[0-2]|0[1-9])/,
          day = /(3[01]|0[1-9]|[12][0-9])/,
          hour = /(2[0-3]|[01][0-9])/,
          minute = /([0-5][0-9])/,
          second = /([0-5][0-9])/,
          ms = /(\.[0-9]+)/,
          timezone = /(Z|[+\-](?:2[0-3]|[01][0-9]):[0-5][0-9])/,
          date = [year.source, month.source, day.source].join('-'),
          time = [hour.source, minute.source, second.source].join(':'),
          timestampRegex,
          result;
  
      timestampRegex = new RegExp(
          '^' + date + '(T' + time + ms.source + '?' + timezone.source + ')?$'
      );
  
      result = timestampRegex.exec(timestamp);
  
      return result !== null;
  }