The format keyword arguments were mismatched between human and delta2human.

The name of these arguments is still up for discussion.

README.rst

@@ -40,7 +40,7 @@ You really only need to worry about *human*.
 
 Here are all the available arguments and defaults::
 
- human(d, precision=2, format_past='{0} ago', format_future='in {0}'):
+ human(d, precision=2, past_format='{0} ago', future_format='in {0}'):
 
 d
  datetime object to make into human readable, required
@@ -48,10 +48,10 @@ d
 precision
  control how verbose the output should look, optional
 
-format_past
+past_format
  format string used when d is a past datetime, optional
 
-format_future
+future_format
  format string used when d is a future datetime, optional
 
 
@@ -99,16 +99,16 @@ Now we will document how to use delta2human and delta2dict::
  # create a dictionary out of the timedelta
  print delta2dict( delta )
 
-Example format_past and format_future keyword arguments::
+Example past_format and future_format keyword arguments::
 
  output1 = human( PAST,
-   format_past = 'titanic sunk {0} ago',
-   format_future = 'titanic will sink in {0} from now'
+   past_format = 'titanic sunk {0} ago',
+   future_format = 'titanic will sink in {0} from now'
  )
 
  output2 = human( FUTURE,
-   format_past = 'titanic sunk {0} ago',
-   format_future = 'titanic will sink in {0} from now'
+   past_format = 'titanic sunk {0} ago',
+   future_format = 'titanic will sink in {0} from now'
  )
 
  print output1

ago.py

@@ -30,10 +30,10 @@ def delta2human(delta, precision=2, past_format='{0} ago', future_format='in {0}
     human_delta = ', '.join( hlist )
     return the_format.format(human_delta) 
 
-def human(d, precision=2, format_past='{0} ago', format_future='in {0}'):
+def human(d, precision=2, past_format='{0} ago', future_format='in {0}'):
     """Pass datetime we will return human delta string"""
     delta = datetime.now() - d
-    return delta2human( delta, precision, format_past, format_future ) 
+    return delta2human( delta, precision, past_format, future_format ) 
 
 if __name__ == "__main__": 
     from test_ago import test_output

test_ago.py

@@ -43,15 +43,15 @@ def test_two_day_plural():
 
 def test_past_format():
     output = human( PAST,
-      format_past = 'titanic sunk {0} ago',
-      format_future = 'titanic will sink in {0} from now'
+      past_format = 'titanic sunk {0} ago',
+      future_format = 'titanic will sink in {0} from now'
     )
     assert 'titanic sunk' in output
 
 def test_future_format():
     output = human( FUTURE,
-      format_past = 'titanic sunk {0} ago',
-      format_future = 'titanic will sink in {0} from now'
+      past_format = 'titanic sunk {0} ago',
+      future_format = 'titanic will sink in {0} from now'
     )
     assert 'titanic will sink in' in output
 
@@ -69,11 +69,11 @@ def test_output():
     print '\nTesting past:\n'
     print delta2dict( PAST_DELTA )
     print 'Commented ' + delta2human( PAST_DELTA, 3 )
-    print human( PAST, format_past = "Commented {0} ago" )
+    print human( PAST, past_format = "Commented {0} ago" )
 
     print '\nTesting future:\n'
     print delta2dict( FUTURE_DELTA )
     print 'Shutdown ' + delta2human( FUTURE_DELTA, 3 )
-    print human( FUTURE, format_future = 'Shutdown in {0} from now' )
+    print human( FUTURE, future_format = 'Shutdown in {0} from now' )
     print ''