diff --git a/endpoints/api/tag.py b/endpoints/api/tag.py
index f7fe496d4..af44132d5 100644
--- a/endpoints/api/tag.py
+++ b/endpoints/api/tag.py
@@ -35,11 +35,11 @@ def _tag_dict(tag):
     tag_info['size'] = tag.legacy_image.aggregate_size
 
   if tag.lifetime_start_ts > 0:
-    last_modified = format_date(datetime.fromtimestamp(tag.lifetime_start_ts))
+    last_modified = format_date(datetime.utcfromtimestamp(tag.lifetime_start_ts))
     tag_info['last_modified'] = last_modified
 
   if tag.lifetime_end_ts is not None:
-    expiration = format_date(datetime.fromtimestamp(tag.lifetime_end_ts))
+    expiration = format_date(datetime.utcfromtimestamp(tag.lifetime_end_ts))
     tag_info['expiration'] = expiration
 
   return tag_info