Retrieve a time stamp of the info page from a patch date header

time.spec

@@ -1,7 +1,7 @@
 Summary:    A GNU utility for monitoring a program's use of system resources
 Name:       time
 Version:    1.9
-Release:    14%{?dist}
+Release:    15%{?dist}
 # src/time.c:               GPLv3+
 # COPYING:                  GPLv3 text
 # doc/time.texi:            GFDL
@@ -63,9 +63,8 @@ BuildRequires:  coreutils
 BuildRequires:  gcc
 BuildRequires:  gnupg2
 BuildRequires:  make
-BuildRequires:  texinfo
-# Tests
 BuildRequires:  sed
+BuildRequires:  texinfo
 
 %description
 The GNU time utility runs another program, collects information about
@@ -79,7 +78,7 @@ the results.
 %patch1 -p1
 %patch2 -p1
 # Set time stamp stored in an info page to the latest patch
-touch -r %{PATCH2} doc/time.texi
+touch -d "$(sed -n -e '/^Date: /{s/^[^:]*: //;p}' %{PATCH2})" doc/time.texi
 %patch3 -p1
 # Correct version VERSION flag for doc/time.texi
 # <https://lists.gnu.org/archive/html/bug-time/2021-01/msg00000.html>
@@ -106,6 +105,9 @@ rm -f $RPM_BUILD_ROOT%{_infodir}/dir
 # time(1) manual page lives in man-pages package, bug #1612294.
 
 %changelog
+* Wed Jan 13 2021 Petr Pisar <ppisar@redhat.com> - 1.9-15
+- Retrieve a time stamp of the info page from a patch date header
+
 * Wed Jan 13 2021 Petr Pisar <ppisar@redhat.com> - 1.9-14
 - Correct version in an info page
 - Set time stamp stored in an info page to the latest patch