Cupcake, use this one here:

alias countdown {
  noop $$?="How many minutes apart would you like me to announce the countdown?"
  var %c amsg $!duration($calc($ctime(Jan 01 2011 12:00) - $!ctime))
  $+(.timercd,$cid,$network) 0 $calc($! * 60) % [ $+ [ c ] ] left until New Years Eastern Time.
}