Restore the -n flag parsing, but ignore it.

Since D19668 was done, new users of the -n flag have surfaced. Parse
and ignore it on the command line until they can be updated.

Suggested by: rgrimes (in D19668).

bin/date/date.1

@@ -32,7 +32,7 @@
 .\"     @(#)date.1	8.3 (Berkeley) 4/28/95
 .\" $FreeBSD$
 .\"
-.Dd March 20, 2019
+.Dd April 23, 2019
 .Dt DATE 1
 .Os
 .Sh NAME
@@ -40,7 +40,7 @@
 .Nd display or set date and time
 .Sh SYNOPSIS
 .Nm
-.Op Fl jRu
+.Op Fl jnRu
 .Op Fl r Ar seconds | Ar filename
 .Oo
 .Fl v
@@ -142,6 +142,8 @@ This allows you to use the
 flag in addition to the
 .Cm +
 option to convert one date format to another.
+.It Fl n
+Obsolete flag, accepted and ignored for compatibility.
 .It Fl R
 Use RFC 2822 date and time output format.
 This is equivalent to using

bin/date/date.c

@@ -108,7 +108,7 @@ main(int argc, char *argv[])
 	(void) setlocale(LC_TIME, "");
 	rflag = 0;
 	Iflag = jflag = Rflag = 0;
-	while ((ch = getopt(argc, argv, "f:I::jRr:uv:")) != -1)
+	while ((ch = getopt(argc, argv, "f:I::jnRr:uv:")) != -1)
 		switch((char)ch) {
 		case 'f':
 			fmt = optarg;
@@ -132,6 +132,8 @@ main(int argc, char *argv[])
 		case 'j':
 			jflag = 1;	/* don't set time */
 			break;
+		case 'n':
+			break;
 		case 'R':		/* RFC 2822 datetime format */
 			if (Iflag)
 				multipleformats();