diff --git a/jssg/settings.py b/jssg/settings.py
index 840dd9a..048a99b 100644
--- a/jssg/settings.py
+++ b/jssg/settings.py
@@ -53,7 +53,7 @@
 JFME_TEMPLATES_DIRS = [path / "templates" for path in JFME_CONTENT_DIRS]
 JFME_STATIC_DIRS = [path / "static" for path in JFME_CONTENT_DIRS]
 JFME_NUMBER_OF_POSTS_BY_PAGE = 3
-JFME_SITEMAP_LASTMOD_DATETIME_FORMAT = "%Y-%m-%dT%H:%M:%S%z" # %Y:YYYY, %m:MM, %d:DD, %z:+/-HHMM
+JFME_SITEMAP_LASTMOD_DATETIME_FORMAT = "%Y-%m-%dT%H:%M:%S%z" # strftime format, see https://docs.python.org/fr/3.6/library/datetime.html#strftime-and-strptime-behavior, see https://www.sitemaps.org/protocol.html#lastmoddef for allowed datetime formats
 
 #Django sites and sitemap app
 SITE_ID = 1