Author: Bernhard M. Wiedemann <bwiedemann suse de>
Date: 2019-07-22

Allow to override build date with SOURCE_DATE_EPOCH
in order to make builds reproducible.
See https://reproducible-builds.org/ for why this is good
and https://reproducible-builds.org/specs/source-date-epoch/
for the definition of this variable.

diff --git a/python/mozbuild/mozbuild/action/langpack_manifest.py b/python/mozbuild/mozbuild/action/langpack_manifest.py
index 6f72697..d4cca96 100644
--- a/python/mozbuild/mozbuild/action/langpack_manifest.py
+++ b/python/mozbuild/mozbuild/action/langpack_manifest.py
@@ -16,6 +16,7 @@ import os
 import json
 import io
 import datetime
+import time
 import requests
 import mozversioncontrol
 import mozpack.path as mozpath
@@ -100,7 +101,7 @@ def get_timestamp_for_locale(path):
         dt = get_dt_from_hg(path)
 
     if dt is None:
-        dt = datetime.datetime.utcnow()
+        dt = datetime.datetime.utcfromtimestamp(int(os.environ.get('SOURCE_DATE_EPOCH', time.time())))
 
     dt = dt.replace(microsecond=0)
     return dt.strftime("%Y%m%d%H%M%S")