Managing who gets alerts - shifts and rotations

$ENGLAND=sam

  TIME=0400:1200
       MAIL $ENGLAND

thanks for the input! Doing it this way makes it a lot easier to read,
but it doesn't break into the underlying problem that much, because
the shifts are more complicated. Say, John's 9-5 Monday-Friday.
Nicks's 7-3 four days and 9-5 Saturday. Larry's 4-12 M-F. So We need a
$US Monday 7-9am and Monday 9am-noon and Monday noon-3:00 and so on...
I can imagine the day when we have 168 rule sets.