merged upstream <https://savannah.gnu.org/bugs/?54367>


Index: gettext-0.19.8.1/gettext-tools/src/xgettext.c
===================================================================
--- gettext-0.19.8.1.orig/gettext-tools/src/xgettext.c
+++ gettext-0.19.8.1/gettext-tools/src/xgettext.c
@@ -3714,6 +3714,9 @@ construct_header ()
   char *msgstr;
   char *comment;
   static lex_pos_ty pos = { __FILE__, __LINE__ };
+  char *source_date_epoch;
+  unsigned long long epoch;
+  char *endptr;
 
   if (package_name != NULL)
     {
@@ -3734,7 +3738,31 @@ the MSGID_BUGS_ADDRESS variable there; o
 specify an --msgid-bugs-address command line option.\n\
 ")));
 
-  time (&now);
+  source_date_epoch = getenv("SOURCE_DATE_EPOCH");
+  if (source_date_epoch) {
+   errno = 0;
+   epoch = strtoull(source_date_epoch, &endptr, 10);
+   if ((errno == ERANGE && (epoch == ULLONG_MAX || epoch == 0))
+     || (errno != 0 && epoch == 0)) {
+    fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: strtoull: %s\n", strerror(errno));
+    exit(EXIT_FAILURE);
+   }
+   if (endptr == source_date_epoch) {
+    fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: No digits were found: %s\n", endptr);
+    exit(EXIT_FAILURE);
+   }
+   if (*endptr != '\0') {
+    fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: Trailing garbage: %s\n", endptr);
+    exit(EXIT_FAILURE);
+   }
+   if (epoch > ULONG_MAX) {
+    fprintf(stderr, "Environment variable $SOURCE_DATE_EPOCH: value must be smaller than or equal to %lu but was found to be: %llu \n", ULONG_MAX, epoch);
+    exit(EXIT_FAILURE);
+   }
+   now = epoch;
+  } else {
+   now = time(NULL);
+  }
   timestring = po_strftime (&now);
 
   msgstr = xasprintf ("\
