--- sphinx/util/i18n.py.orig
+++ sphinx/util/i18n.py
@@ -188,7 +188,7 @@ def format_date(format, date=None, language=None, warn=None):
         # See https://wiki.debian.org/ReproducibleBuilds/TimestampsProposal
         source_date_epoch = os.getenv('SOURCE_DATE_EPOCH')
         if source_date_epoch is not None:
-            date = gmtime(float(source_date_epoch))
+            date = datetime.utcfromtimestamp(float(source_date_epoch))
         else:
             date = datetime.now()