crontab

# weekdays
30 21  * * 0-4 Say 'Prepare to go to bed!'
44 21  * * 0-4 Say '2 minutes left'
46 21  * * 0-4 /sbin/ifconfig en0 down; say 'Go to bed!'
*/3 22  * * 0-4 /sbin/ifconfig en0 down; say 'Go to bed'
1 22  * * 0-4 /sbin/ifconfig en0 down; say 'Fifteen minutes remaining'
14 22  * * 0-4 /sbin/ifconfig en0 down; say 'One minute remaining'
*/2 23  * * 0-4 /sbin/ifconfig en0 down; say 'Go to bed'
*/2 0  * * 0-4 /sbin/ifconfig en0 down; say 'Go to bed'
*/1 0  * * 1-5 /sbin/ifconfig en0 down; say 'Go to bed'
*/1 1  * * 1-5 /sbin/ifconfig en0 down; say 'Go to bed'
*/1 2  * * 1-5 /sbin/ifconfig en0 down; say 'Go to bed'
*/1 3  * * 1-5 /sbin/ifconfig en0 down; say 'Go to bed'


# weekends
# Warning at 23:00
# Off at 23:30
# Every 3 minutes at 0:00
00 23  * * 5-6 Say 'Prepare to go to bed!'
30 23  * * 5-6 /sbin/ifconfig en0 down; say 'Go to bed!'
35 23  * * 5-6 /sbin/ifconfig en0 down; say 'Go to bed!'
40 23  * * 5-6 /sbin/ifconfig en0 down; say 'Go to bed!'
45 23  * * 5-6 /sbin/ifconfig en0 down
50 23  * * 5-6 /sbin/ifconfig en0 down
55 23  * * 5-6 /sbin/ifconfig en0 down
*/3 0  * * 6-7 /sbin/ifconfig en0 down; say 'Go to bed'
*/2 1  * * 6-7 /sbin/ifconfig en0 down; say 'Go to bed'
*/1 2  * * 6-7 /sbin/ifconfig en0 down; say 'Go to bed'