README.md in timespan-0.5.3 vs README.md in timespan-0.5.4

@@ -3,11 +3,11 @@
 Use Timespans in Ruby :)
 
 Will calculate time diff between two dates, then allow you to get the time difference in some time unit as a number.
 
 ```ruby
-	t = Timespan.new(:start => Date.today, :duration => 3.days.ago)
+	t = Timespan.new(:start => Date.today, :duration => 3.days)
 	t.to_days # => 3
 	t.to_weeks # => 0
 	t.to_secs # => 259200
 	t.to_hours = 10800
 
@@ -321,9 +321,21 @@
 
 dr.between?(4.days) # => true
 ```
 
 You can also use Range#intersect from *sugar-high* gem to test intersection of time ranges ;)
+
+The duration range by default supports the following units: [seconds, minutes, hours, days, weeks, months, years]
+
+You can subclass the DurationRange to supply your own list of time units to fit your particular scenario.
+
+This gem comes with two subclasses:
+
+`ShortDurationRange` and `LongDurationRange`
+
+They both override the method `#allowed_units` to provide a particular list:
+
+`ShortDurationRange` supports time ranges less than a day, whereas `LongDurationRange` only supports time ranges of a day or more.
 
 ## Client side helpers
 
 This gem now includes som javascript assets to assist in performing date and timespan (duration) calculations on the client side also: