diff --git a/seminar/templatetags/utils.py b/seminar/templatetags/utils.py
index 52610eec..4ba33a0e 100644
--- a/seminar/templatetags/utils.py
+++ b/seminar/templatetags/utils.py
@@ -16,5 +16,5 @@ def kratke_datum(dt):
 	if not isinstance(dt, datetime):
 		logger.warning(f"Špatné volání filtru {__name__}: {dt}")
 		return False
-	out = f'<span title="{dt.strftime("%d. %m. %Y %H:%M")}">{dt.day}.{dt.month}.<span style="text-decoration:overline">{dt.year%100}</span>'
+	out = f'<time datetime="{dt.isoformat()}" title="{dt.strftime("%d. %m. %Y %H:%M")}">{dt.day}.{dt.month}.<span style="text-decoration:overline">{dt.year%100}</time>'
 	return mark_safe(out)