File reproducible.patch of Package lifelines

https://github.com/lifelines/lifelines/pull/389

From 68666c90ba645c08ed3ee7a565ee3951ac43539c Mon Sep 17 00:00:00 2001
From: "Bernhard M. Wiedemann" <bwiedemann@suse.de>
Date: Fri, 6 Dec 2019 18:48:40 +0100
Subject: [PATCH] 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.

Also switch to UTC to be independent of timezone.
Also use ISO 8601 date format to be easier to parse.
This also avoids use of %b that can vary from locales.

This PR was done while working on reproducible builds for openSUSE.
---
 reports/gen_index | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/reports/gen_index b/reports/gen_index
index 0343f87b..2ae4fe84 100644
--- a/reports/gen_index
+++ b/reports/gen_index
@@ -5,6 +5,7 @@
 # January 2003 
 
 use strict;
+use POSIX qw(strftime);
 
 my $debug = 0;		#non-zero to enable debug output
 my $viewoutput = 0;	#non-zero to enable printing output information
@@ -93,7 +94,7 @@ have text identifying the person who generated the report.
 EOF
 }
 sub print_trailer {
-    my $today = `date "+%d %b %Y"`;
+    my $today = strftime("%Y-%m-%d", gmtime($ENV{SOURCE_DATE_EPOCH} || time));
     print OUT  <<EOF
 </DL>
 <center>