OK...Almost a complete re-write, and while it doesn't work the way you wanted, as in starting and stopping the timer at certain times, this does work and has been tested for several times.
Code:
 on me:*:join:#:{
  .timermsg 0 10 tmsg $chan
}
alias tmsg {
  if $time > 19:34:00 || $time < 04:00:00 {
    .msg $1 hello
  }
}
on *:disconnect:{
  .timermsg off
}