code: function getTimestamp() {
      // use `Math.floor()` here to avoid the "Unix Millennium Bug"
      var now = Math.floor(Date.now() / 1000)
  
      // it's another second since the last id were created,
      // so we need to regenerate the timestamp
      if (time !== now) {
          ctr       = 0
          timestamp = pad(time = now, 8, 16)
      }
      // Since changing parts of an identifier are the timestamp and
      // the sequence; the count of maximum allocatable ids in a second
      // is limited by the sequence size (3-bytes = about 16 million).
      // Otherwise uniqueness is not guaranteed.
      else
          assert(++ctr < 0x1000000, 'more than 16 million ids generated in 1 second')
  
      return timestamp
  }
docs: Calculate the current timestamp if needed,
  otherwise return the last cached one.
  
  @return {string}