diff --git a/utils/serializers.py b/utils/serializers.py
index 3632e72f22eafe51fc7c3e35cf9ace41f820fb58..51135d8fec602f92526bcc7c498283ed6c0c4f39 100644
--- a/utils/serializers.py
+++ b/utils/serializers.py
@@ -4,7 +4,7 @@ import pytz
 # cf. https://stackoverflow.com/questions/30313243/messagepack-and-datetime
 def decode_datetime(obj):
     if '__datetime__' in obj.keys():
-        tmp = datetime.datetime.strptime(obj["as_str"], "%Y-%m-%dT%H:%M:%S.%fZ")
+        tmp = datetime.datetime.strptime(obj["as_str"], "%Y-%m-%dT%H:%M:%SZ")
         output = pytz.timezone('UTC').localize(tmp)
     elif '__date__' in obj.keys():
         output = datetime.datetime.strptime(obj["as_str"], "%Y-%m-%d")
@@ -24,7 +24,7 @@ def encode_datetime(obj):
 
         tmp2 = tmp1.astimezone(pytz.UTC)
 
-        return {'__datetime__': True, 'as_str': tmp2.strftime("%Y-%m-%dT%H:%M:%S.%fZ")}
+        return {'__datetime__': True, 'as_str': tmp2.strftime("%Y-%m-%dT%H:%M:%SZ")}
 
     if isinstance(obj, datetime.date):
         return {'__date__': True, 'as_str': obj.strftime("%Y-%m-%d")}