code: public static BucketFunction age(long max, TimeUnit unit) {
      return wrap(com.netflix.spectator.api.histogram.BucketFunctions.age(max, unit));
    }
docs: Returns a function that maps age values to a set of buckets. Example use-case would be
  tracking the age of data flowing through a processing pipeline. Values that are less than
  0 will be marked as "future". These typically occur due to minor variations in the clocks
  across nodes. In addition to a bucket at the max, it will create buckets at max / 2, max / 4,
  and max / 8.
  
  @param max
  Maximum expected age of data flowing through. Values greater than this max will be mapped
  to an "old" bucket.
  @param unit
  Unit for the max value.
  @return
  Function mapping age values to string labels. The labels for buckets will sort
  so they can be used with a simple group by.