This is standard unix calendar program for Linux, ported from OpenBSD.

While porting I removed all code for mailing calendar to users (-a).
If you still need it, just do something like this:

awk 'BEGIN{ FS = ":" } { if($7=="/bin/bash") print $1 }' </etc/passwd |(
while read user; do
    su $user -c "calendar | mail $user"
done
)

NOTE: I've never tested this!

Thanks to all OpenBSD developers for good OS and especially for good 
calendar program.

Andrey Ulanov <drey@rt.mipt.ru>
$Id: README,v 1.3 2002/11/27 07:58:46 drey Exp $
