diff --git a/addons/resource/models/resource.py b/addons/resource/models/resource.py
index ddb3238320a..ddf68e079bf 100644
--- a/addons/resource/models/resource.py
+++ b/addons/resource/models/resource.py
@@ -34,7 +34,7 @@ def to_naive_utc(datetime, record):
 
 
 def to_tz(datetime, tz_name):
-    tz = pytz.timezone(tz_name)
+    tz = pytz.timezone(tz_name) if tz_name else pytz.UTC
     return pytz.UTC.localize(datetime.replace(tzinfo=None), is_dst=False).astimezone(tz).replace(tzinfo=None)