diff --git a/doc/source/v0.14.0.txt b/doc/source/v0.14.0.txt
index a484fa3a1f656..bca270856e41b 100644
--- a/doc/source/v0.14.0.txt
+++ b/doc/source/v0.14.0.txt
@@ -330,6 +330,7 @@ Enhancements
   and data_label which allow the time stamp and dataset label to be set when creating a
   file. (:issue:`6545`)
 - ``pandas.io.gbq`` now handles reading unicode strings properly. (:issue:`5940`)
+- For a DatetimeIndex ``freq`` always tries to infer a frequency. If it is possible to infer the frequency, viewing the ``inferred_freq`` property of a DatetimeIndex will now also set the offset and freq property as a side effect.
 
 Performance
 ~~~~~~~~~~~
diff --git a/pandas/tseries/index.py b/pandas/tseries/index.py
index c58447acec621..26f7cc93e685f 100644
--- a/pandas/tseries/index.py
+++ b/pandas/tseries/index.py
@@ -1421,12 +1421,17 @@ def map(self, f):
     @property
     def freq(self):
         """ return the frequency object if its set, otherwise None """
+        offset = self.offset
+        if offset is None:
+            _ = self.inferred_freq
         return self.offset
 
     @cache_readonly
     def inferred_freq(self):
         try:
-            return infer_freq(self)
+            freq = infer_freq(self)
+            self.offset = to_offset(freq)
+            return freq
         except ValueError:
             return None