diff --git a/src/gphotos_sync/authorize.py b/src/gphotos_sync/authorize.py
index 488ad2f6..ea7b1441 100644
--- a/src/gphotos_sync/authorize.py
+++ b/src/gphotos_sync/authorize.py
@@ -2,6 +2,7 @@
 from json import JSONDecodeError, dump, load
 from pathlib import Path
 from typing import List, Optional
+from datetime import timezone
 
 from google_auth_oauthlib.flow import InstalledAppFlow
 from requests.adapters import HTTPAdapter
@@ -104,7 +105,7 @@ def authorize(self):
                 "refresh_token": flow.credentials.refresh_token,
                 "token_type": "Bearer",
                 "scope": flow.credentials.scopes,
-                "expires_at": flow.credentials.expiry.timestamp(),
+                "expires_at": flow.credentials.expiry.replace(tzinfo=timezone.utc).timestamp()
             }
 
             self.save_token(oauth2_token)