From <https://github.com/bmwiedemann/psm/commit/98acae1a6f2c9b2e6014eac4070a817c9d0fd8a2>.

From 98acae1a6f2c9b2e6014eac4070a817c9d0fd8a2 Mon Sep 17 00:00:00 2001
From: "Bernhard M. Wiedemann" <bwiedemann@suse.de>
Date: Sun, 23 Jul 2017 07:02:28 +0200
Subject: [PATCH] Allow to override build date

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 uses UTC to be independent of timezone settings.
---
 Makefile       | 2 +-
 ipath/Makefile | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index d79c4bd..99406ef 100644
--- a/Makefile
+++ b/Makefile
@@ -270,7 +270,7 @@ ${TARGLIB}.so.${MAJOR}: ${TARGLIB}.so.${MAJOR}.${MINOR}
 # file around.  Generate it such that the ident command can find it
 # and strings -a | grep InfiniPath does a reasonable job as well.
 ${TARGLIB}.so.${MAJOR}.${MINOR}: ${${TARGLIB}-objs}
-	date +'char psmi_infinipath_revision[] ="$$""Date: %F %R ${rpm_extra_description}InfiniPath $$";' > ${lib_build_dir}/_revision.c
+	date -u -d@$${SOURCE_DATE_EPOCH:-$$(date +%s)} +'char psmi_infinipath_revision[] ="$$""Date: %F %R ${rpm_extra_description}InfiniPath $$";' > ${lib_build_dir}/_revision.c
 	$(CC) -c $(BASECFLAGS) $(INCLUDES) _revision.c -o _revision.o
 	$(CC) $(LDFLAGS) -o $@ -Wl,-soname=${TARGLIB}.so.${MAJOR} -shared -Wl,--unique='*fastpath*' \
 		${${TARGLIB}-objs} _revision.o -L$(build_dir)/ipath $(LDLIBS)
diff --git a/ipath/Makefile b/ipath/Makefile
index 8c2cc6e..73abd6f 100644
--- a/ipath/Makefile
+++ b/ipath/Makefile
@@ -70,7 +70,7 @@ ${TARGLIB}.so.${MAJOR}: ${TARGLIB}.so.${MAJOR}.${MINOR}
 # file around.  Generate it such that the ident command can find it
 # and strings -a | grep InfiniPath does a reasonable job as well.
 ${TARGLIB}.so.${MAJOR}.${MINOR}: ${${TARGLIB}-objs}
-	date +'static __attribute__ ((unused)) char __psc_infinipath_revision[] ="$$""Date: %F %R ${rpm_extra_description}InfiniPath $$";' > _revision.c
+	date -u -d@$${SOURCE_DATE_EPOCH:-$$(date +%s)} +'static __attribute__ ((unused)) char __psc_infinipath_revision[] ="$$""Date: %F %R ${rpm_extra_description}InfiniPath $$";' > _revision.c
 	$(CC) -c $(BASECFLAGS) $(INCLUDES) _revision.c -o _revision.o
 	$(CC) -o $@ -Wl,-soname=${TARGLIB}.so.${MAJOR} -shared \
 		-Wl,--unique='*fastpath*' \
><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/packages/gsasl.scm?id=0e001b1f412d26937eb7cc616dab6b8a8b6beeee&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-04-30 12:50:06 -0400'>2020-04-30</span></td><td><a href='/guix/commit/gnu/packages/gsasl.scm?id=194cb75d85a2d282419b2a618c8e124f140859f3'>gnu: libntlm: Update to 1.6 [fixes CVE-2019-17455].</a><span class='msg-avail'>...</span></td><td>Simon Josefsson</td></tr>
<tr><td><span title='2020-01-23 22:43:46 +0100'>2020-01-23</span></td><td><a href='/guix/commit/gnu/packages/gsasl.scm?id=10214fa9f637a6c780ccca1710413e67fe9b3d83'>gnu: gsasl: Do not build 'libgsasl.a'.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-01-23 22:43:46 +0100'>2020-01-23</span></td><td><a href='/guix/commit/gnu/packages/gsasl.scm?id=df8a9c7496c82f56560ce5e84c2c27c83010e64d'>gnu: gsasl: Update to 1.8.1.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>