date & touch: timegm/mktime checks

Another bunch of straightforward changes. The checks in touch don't make
that code prettier, though.

Index: bin/date/date.c
===================================================================
RCS file: /cvs/src/bin/date/date.c,v
diff -u -p -r1.60 date.c
--- bin/date/date.c	28 Apr 2024 16:43:15 -0000	1.60
+++ bin/date/date.c	21 Jun 2026 08:03:07 -0000
@@ -223,11 +223,12 @@ setthetime(char *p, const char *pformat)
 	}
 
 	/* convert broken-down time to UTC clock time */
+	lt->tm_wday = -1;
 	if (pformat != NULL && strstr(pformat, "%s") != NULL)
 		tval = timegm(lt);
 	else
 		tval = mktime(lt);
-	if (tval == -1)
+	if (tval == -1 && lt->tm_wday == -1)
 		errx(1, "specified date is outside allowed range");
 
 	if (jflag)
Index: usr.bin/touch/touch.c
===================================================================
RCS file: /cvs/src/usr.bin/touch/touch.c,v
diff -u -p -r1.27 touch.c
--- usr.bin/touch/touch.c	29 Jan 2022 00:06:26 -0000	1.27
+++ usr.bin/touch/touch.c	21 Jun 2026 08:06:55 -0000
@@ -223,8 +223,9 @@ stime_arg1(char *arg, struct timespec *t
 	}
 
 	lt->tm_isdst = -1;		/* Figure out DST. */
+	lt->tm_wday = -1;
 	tsp[0].tv_sec = tsp[1].tv_sec = mktime(lt);
-	if (tsp[0].tv_sec == -1)
+	if (tsp[0].tv_sec == -1 && lt->tm_wday == -1)
 terr:		errx(1,
 	"out of range or illegal time specification: [[CC]YY]MMDDhhmm[.SS]");
 
@@ -264,8 +265,9 @@ stime_arg2(char *arg, int year, struct t
 	lt->tm_sec = 0;
 
 	lt->tm_isdst = -1;		/* Figure out DST. */
+	lt->tm_wday = -1;
 	tsp[0].tv_sec = tsp[1].tv_sec = mktime(lt);
-	if (tsp[0].tv_sec == -1)
+	if (tsp[0].tv_sec == -1 && lt->tm_wday == -1)
 terr:		errx(1,
 	"out of range or illegal time specification: MMDDhhmm[YY]");
 
@@ -323,8 +325,9 @@ stime_argd(char *arg, struct timespec *t
 		goto terr;
 
 	tm.tm_isdst = -1;
+	tm.tm_wday = -1;
 	tsp[0].tv_sec = utc ? timegm(&tm) : mktime(&tm);
-	if (tsp[0].tv_sec == -1)
+	if (tsp[0].tv_sec == -1 && tm.tm_wday == -1)
 terr:		errx(1,
   "out of range or illegal time specification: YYYY-MM-DDThh:mm:ss[.frac][Z]");
 	tsp[1] = tsp[0];