Use options to control jQuery plugin

You should use wp_localize_script() after enqueuing your JS file that calls the countdown method. I’m assuming you stored the date in an option called date_name like January 1, 2015 13:30:00.

In your case, you are storing it as an array with month, day, year, and time in the correct format, so you should convert it to the January 1, 2015 13:30:00 format.

wp_enqueue_script( 'jsfilename' );
$stored_date = get_option( 'date_name', 'default value' );
// process stored date so that it gets to the January 1, 2015 13:30:00 format
$date_options = array( 'mydate' => $stored_date );
wp_localize_script( 'jsfilename', 'dateopts', $date_options );

Then in your JS file, you call:

$('.live-countdown').countdown({ date: dateopts.mydate });