Centrally-Configure Kartra Countdown Timers

<!--
Centrally-Configured Fixed-Date-And-Time Countdown Timer For Kartra

1. Upload a *plain-text* file containing the event time and expiration redirect URL
(if desired) in this format to the Membership > Files area:

eventTime = '2023-05-20T15:00Z'; /* Event date & GMT/UTC time in ISO format */
expirationURL = 'https://example.com'; /* = ''; for no expiration redirect */
resetTimers();

2. Create a tracking link pointing to the configuration file. Reuse this link on all pages
that should share this timer. Just update the target file URL to the new upload URL if/when
updating the configuration.
3. Add 1+ fixed-date-and-time countdowns to your page with a past date and no redirection.
4. Add this code to the BODY tracking section of your page, putting the tracking link URL
from step 2 into the script src attribute at the bottom.
-->
<script>
var eventTime, expirationURL, counters = $('[data-countdown] div.countdown').attr('data-date', null);
function resetTimers () {
if (!eventTime) return;
var diffSecs = Math.max(Math.floor((+new Date(eventTime) - new Date()) / 1000), 0);
if (diffSecs <= 0 && expirationURL) location = expirationURL;
counters.each((n, el) => {
var $el = $(el);
$el.stopCountDown();
$el.data('diffSecs', diffSecs);
if (expirationURL) $el.data('callback', () => location = expirationURL);
$el.startCountDown();
});
}
$(() => setTimeout(resetTimers, 0));
</script>
<script src='https://account.krtra.com/tracking_link_here' async defer></script>