If the -f argument includes %s, we need to use timegm(3) rather

than mktime(3) because the UNIX Epoch is defined in UTC rather than
in the local timezone.

Combining %s with other format specifiers is usually not useful.
But if a user does that, then parsing the whole input as UTC seems
better than parsing some of it as UTC and some of it in the local
time zone.

Bug found by Bryan Vyhmeister.
The final patch is joint work with and OK by gerhard@.
No objection when shown on tech@.

1 files changed, 6 insertions, 2 deletions

diff --git a/bin/date/date.c b/bin/date/date.c
index b197648716c..635c3f006d0 100644
--- a/bin/date/date.c
+++ b/bin/date/date.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: date.c,v 1.56 2019/08/08 02:17:51 cheloha Exp $	*/
+/*	$OpenBSD: date.c,v 1.57 2021/08/11 13:41:48 schwarze Exp $	*/
 /*	$NetBSD: date.c,v 1.11 1995/09/07 06:21:05 jtc Exp $	*/
 
 /*
@@ -219,7 +219,11 @@ setthetime(char *p, const char *pformat)
 	}
 
 	/* convert broken-down time to UTC clock time */
-	if ((tval = mktime(lt)) == -1)
+	if (pformat != NULL && strstr(pformat, "%s") != NULL)
+		tval = timegm(lt);
+	else
+		tval = mktime(lt);
+	if (tval == -1)
 		errx(1, "specified date is outside allowed range");
 
 	if (jflag)