use macro for /usr/local/plan9
diff --git a/man/man1/calendar.1 b/man/man1/calendar.1
index 1c6b3be..9a9e20e 100644
--- a/man/man1/calendar.1
+++ b/man/man1/calendar.1
@@ -50,4 +50,4 @@
 .B /usr/$user/lib/calendar
 personal calendar
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/calendar.c
+.B \*9/src/cmd/calendar.c