diff --git a/maya/core.py b/maya/core.py
index 042bfd8..423fb2c 100644
--- a/maya/core.py
+++ b/maya/core.py
@@ -578,7 +578,7 @@ def now():
     return MayaDT(epoch=epoch)
 
 
-def when(string, timezone='UTC'):
+def when(string, timezone='UTC', prefer_past=False):
     """"Returns a MayaDT instance for the human moment specified.
 
     Powered by dateparser. Useful for scraping websites.
@@ -589,10 +589,15 @@ def when(string, timezone='UTC'):
     Keyword Arguments:
         string -- string to be parsed
         timezone -- timezone referenced from (default: 'UTC')
+        prefer_past -- prefer parsing ambiguous date as in the past
 
     """
-    dt = dateparser.parse(string,
-                          settings={'TIMEZONE': timezone, 'RETURN_AS_TIMEZONE_AWARE': True, 'TO_TIMEZONE': 'UTC'})
+    settings = {'TIMEZONE': timezone, 'RETURN_AS_TIMEZONE_AWARE': True, 'TO_TIMEZONE': 'UTC'}
+
+    if prefer_past:
+        settings['PREFER_DATES_FROM'] = 'past'
+    
+    dt = dateparser.parse(string, settings=settings)
 
     if dt is None:
         raise ValueError('invalid datetime input specified.')
diff --git a/tests/test_maya.py b/tests/test_maya.py
index a28a54a..4b5fce8 100644
--- a/tests/test_maya.py
+++ b/tests/test_maya.py
@@ -170,6 +170,17 @@ def test_parse():
     d = maya.parse('01/05/2016', day_first=True)
     assert format(d) == '2016-05-01 00:00:00+00:00'
 
+def test_when_past():
+    next_month = str(maya.now().add(months=1).month)
+    this_year = maya.now().year
+    last_year = this_year - 1
+
+    future_date = maya.when(next_month)
+    past_date = maya.when(next_month, prefer_past=True)
+
+    assert future_date.year == this_year
+    assert past_date.year == last_year
+
 
 def test_datetime_to_timezone():
     dt = maya.when('2016-01-01').datetime(to_timezone='US/Eastern')