From: Matthias Kilian <kili@outback.escape.de>
Subject: Re: newsyslog
To: Alvar Penning <post@0x21.biz>
Cc: tech@openbsd.org
Date: Wed, 1 Apr 2026 23:30:37 +0200

Hi,

On Wed, Apr 01, 2026 at 10:41:28PM +0200, Alvar Penning wrote:
> diff --git a/newsyslog.c b/newsyslog.c
> index 0be4ed259b9..d4a62194ab3 100644
> --- a/newsyslog.c
> +++ b/newsyslog.c
> @@ -1251,12 +1251,12 @@ parseDWM(char *s)
>  
>  	nd = mtab[tm.tm_mon];
>  
> -	if (tm.tm_mon == 1) {
> -		if (((tm.tm_year + 1900) % 4 == 0) &&
> -		    ((tm.tm_year + 1900) % 100 != 0) &&
> -		    ((tm.tm_year + 1900) % 400 == 0)) {
> -			nd++;	/* leap year, 29 days in february */
> -		}
> +	/* leap year, 29 days in february */
> +	if ((tm.tm_mon == 1) && ((tm.tm_year + 1900) % 4 == 0)) {
> +		if ((tm.tm_year + 1900) % 100 != 0)
> +			nd++; /* divisible by 4, not divisible by 100 */
> +		else if ((tm.tm_year + 1900) % 400 == 0)
> +			nd++; /* divisible by 4, 100 and 400 */
>  	}
>  	tm.tm_hour = tm.tm_min = tm.tm_sec = 0;

While this looks correct to me, wouldn't something like this be
better?

--- newsyslog.c	Tue Sep 23 08:09:56 2025
+++ newsyslog.c.new	Wed Apr  1 23:28:07 2026
@@ -1253,8 +1253,8 @@
 
 	if (tm.tm_mon == 1) {
 		if (((tm.tm_year + 1900) % 4 == 0) &&
-		    ((tm.tm_year + 1900) % 100 != 0) &&
-		    ((tm.tm_year + 1900) % 400 == 0)) {
+		    (((tm.tm_year + 1900) % 100 != 0) ||
+		     ((tm.tm_year + 1900) % 400 == 0))) {
 			nd++;	/* leap year, 29 days in february */
 		}
 	}

Ciao,
	Kili