add_action('cred_save_data', 'tssupp_form_submit', 10, 2);
function tssupp_form_submit($post_id, $form_data)
{
// Edit
$start_form_id = 83; // ID of form with start time
$end_form_id = 130; // ID of form with end time
$start = 'date-d-entree'; // slug of start field
$end = 'date-de-sortie'; // slug of end field
// Types date field expects date to be stored as "local" timestamp
$site_timezone = get_option('Europe/Paris');
$timezone_offset_in_seconds = timezone_offset_get(timezone_open($site_timezone), new DateTime());
$now = time() + $timezone_offset_in_seconds;
This isn't correct and you can revert that line back to how Nigel shared it.
What he meant was that you should go to your website's WP Admin -> Settings -> General and make sure that "Paris" is selected in the "Timezone" option.
Note: In case the website still shows "le site rencontre des problemetitle" error, after reverting to the Nigel's original code, please enable WordPress debugging on ( ref: https://wordpress.org/support/article/debugging-in-wordpress/ ) and let us know if there any errors/warnings shown on the screen or in server's error log.
It looks like the original issue is resolved, and as this thread has become very long I've split the follow-up question into a new thread and I'll answer there.
To make the forums searchable by other users with related issues we try to limit the threads to a single issue.