https://github.com/marshmallow-code/marshmallow/pull/679.patch

From 8064d7e155a78cde6e7a2387ec365dcf0798641d Mon Sep 17 00:00:00 2001
From: "Bernhard M. Wiedemann" <bwiedemann@suse.de>
Date: Sun, 24 Sep 2017 21:54:43 +0200
Subject: [PATCH] Use Changelog date instead of build date

in order to make builds reproducible.
See https://reproducible-builds.org/ for why this is good.
---
 docs/conf.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: marshmallow-2.19.2/docs/conf.py
===================================================================
--- marshmallow-2.19.2.orig/docs/conf.py
+++ marshmallow-2.19.2/docs/conf.py
@@ -57,7 +57,7 @@ master_doc = 'index'
 # General information about the project.
 project = u'marshmallow'
 copyright = ' {0:%Y} <a href="https://stevenloria.com">Steven Loria</a>'.format(
-    dt.datetime.utcnow()
+    dt.datetime.utcfromtimestamp(os.path.getmtime('../CHANGELOG.rst'))
 )
 
 version = release = marshmallow.__version__