diff --git a/plio/io/io_json.py b/plio/io/io_json.py
index 161a68e4c0c102f3965753074bd98394b98390d3..470d09144e9e87df521470a4e95bc3ecadc7fa5f 100644
--- a/plio/io/io_json.py
+++ b/plio/io/io_json.py
@@ -1,6 +1,6 @@
 import json
 import numpy as np
-
+import datetime
 
 class NumpyEncoder(json.JSONEncoder):
     def default(self, obj):
@@ -9,7 +9,7 @@ class NumpyEncoder(json.JSONEncoder):
         elif isinstance(obj, datetime.date):
             return obj.isoformat()
         return json.JSONEncoder.default(self, obj)
-
+ 
 def read_json(inputfile):
     """
     Read the input json file into a python dictionary.