Javascript countdown timer

Nothing too fancy here, but potentially useful to people. The other day a forum I maintain needed a way for users to add a countdown timer to their posts, so I wrote this bit of Javascript and added it as a new BBCode. Feel free to use it and share it.

The help text

[countdown]year, month, day, hour, min, sec[/countdown]

The date/time must be specified in UTC (GMT). sec is optional.

The BBCode

[countdown]{SIMPLETEXT}[/countdown]

The replacement text

<script type="text/javascript""countdown_timer"" has_timer""""0"":""0"":""0""time expired"