on 6/7 2008, can't match "the first saturday  task"

Reference: /n/sources/patch/applied/calendar-nth-off1
Date: Fri Jun  6 18:38:14 CES 2008
Signed-off-by: lufia@lufia.org

--- /sys/src/cmd/calendar.c	Fri Jun  6 18:35:29 2008
+++ /sys/src/cmd/calendar.c	Fri Jun  6 18:35:24 2008
@@ -198,7 +198,7 @@
 	nd->next = Base;	
 	Base = nd;
 
-	snprint(buf, sizeof buf, "[\t ]*the[\t ]+%s[\t ]+%s", nth[tm->mday/7], day);
+	snprint(buf, sizeof buf, "[\t ]*the[\t ]+%s[\t ]+%s", nth[(tm->mday-1)/7], day);
 	if(debug)
 		print("%s\n", buf);
 	nd = emalloc(sizeof(Date));