diff --git a/debian/control b/debian/control
index 71191b69..12a34020 100644
--- a/debian/control
+++ b/debian/control
@@ -16,7 +16,8 @@ Depends: ${misc:Depends}, ${python:Depends},
     python-gnupg,
     python-gevent-websocket,
     python-argcomplete,
-    python-psutil
+    python-psutil,
+    python-tz
 Replaces: yunohost-cli
 Breaks: yunohost-cli
 Description: prototype interfaces with ease in Python
diff --git a/moulinette/interfaces/cli.py b/moulinette/interfaces/cli.py
index fe382216..edff5346 100644
--- a/moulinette/interfaces/cli.py
+++ b/moulinette/interfaces/cli.py
@@ -103,6 +103,8 @@ def pretty_date(_date):
     Argument:
         - date -- The date or datetime to display
     """
+    if _date.tzinfo is None:
+        _date = _date.replace(tzinfo=pytz.utc)
     if time.daylight:
         offsetHour = time.altzone / 3600
     else:
diff --git a/moulinette/utils/serialize.py b/moulinette/utils/serialize.py
index 800cf1b0..0fbea631 100644
--- a/moulinette/utils/serialize.py
+++ b/moulinette/utils/serialize.py
@@ -1,6 +1,7 @@
 import logging
 from json.encoder import JSONEncoder
 import datetime
+import pytz
 
 logger = logging.getLogger('moulinette.utils.serialize')
 
@@ -26,7 +27,9 @@ class JSONExtendedEncoder(JSONEncoder):
             return list(o)
 
         # Display the date in its iso format ISO-8601 Internet Profile (RFC 3339)
-        if isinstance(o, datetime.datetime) or isinstance(o, datetime.date):
+        if isinstance(o, datetime.date):
+            if o.tzinfo is None:
+                o = o.replace(tzinfo=pytz.utc)
             return o.isoformat()
 
         # Return the repr for object that json can't encode