Year change only after annual event held

This is a very specific use case @paulryken .

You can use this into your child theme’s functions.php or Code Snippets plugin.

add_shortcode('specialdate', 'dmyip_rmd_specialdate');
function dmyip_rmd_specialdate($atts) {
    // Set default attributes and merge with user input
    $attributes = shortcode_atts(array(
        'floor_date' => 'today',
        'ceiling_date' => 'last sunday of january next year'
    ), $atts);

    // Parse the floor date using strtotime
    $floor_date = strtotime($attributes['floor_date']);
    if (!$floor_date) {
        return ''; // Clear any error messages
    }

    // Parse the ceiling date using strtotime
    $ceiling_date = strtotime($attributes['ceiling_date']);
    if (!$ceiling_date) {
        return ''; // Clear any error messages
    }

    // Calculate the ceiling date next year
    $ceiling_date_next_year = strtotime('+1 year', $floor_date);

    // Get today's date
    $today = time();

    // Determine if today's date is between the floor date and the ceiling date next year
    if ($today >= $floor_date && $today <= $ceiling_date_next_year) {
        // Format the ceiling date with day, month, and year
        $display_date = date_i18n('j F Y', $ceiling_date);
        return esc_html($display_date);
    }

    return '';
}

add_shortcode('specialyear', 'dmyip_rmd_specialyear');
function dmyip_rmd_specialyear($atts) {
    // Set default attributes and merge with user input
    $attributes = shortcode_atts(array(
        'floor_date' => 'today',
        'ceiling_date' => 'last sunday of january next year'
    ), $atts);

    // Parse the floor date using strtotime
    $floor_date = strtotime($attributes['floor_date']);
    if (!$floor_date) {
        return ''; // Clear any error messages
    }

    // Parse the ceiling date using strtotime
    $ceiling_date = strtotime($attributes['ceiling_date']);
    if (!$ceiling_date) {
        return ''; // Clear any error messages
    }

    // Calculate the ceiling date next year
    $ceiling_date_next_year = strtotime('+1 year', $floor_date);

    // Get today's date
    $today = time();

    // Determine if today's date is between the floor date and the ceiling date next year
    if ($today >= $floor_date && $today <= $ceiling_date_next_year) {
        // Format the ceiling date to show just the year
        $display_year = date_i18n('Y', $ceiling_date);
        return esc_html($display_year);
    }

    return '';
}

It has two components.

[specialdate ceiling_date="last sunday of january next year"] will show the full date like 28 January 2025.

[specialyear ceiling_date="last sunday of january next year"] will just show 2025.

In the ceiling_date argument you can ask for dates in natural language.

Let me know if this works.

I will be adding this to the plugin as well but only after someone else asks for it.

Thank you for this. You have prompted me to review the options. I also use ACF by WPEngine so created a custom field and added the following code to my functions.php.

function update_event_year_in_title($title) {
if (is_singular('post')) { // Replace 'post' with your custom post type if needed
$event_date = get_field('event_date');
if ($event_date) {

// Convert the event date to a timestamp using the correct format
$event_timestamp = DateTime::createFromFormat('d/m/Y', $event_date)->getTimestamp();
$current_timestamp = current_time('timestamp');
       
 // Get the event year from the event date
        $event_year = date('Y', $event_timestamp);

        // Get the current year
        $current_year = date('Y', $current_timestamp);

        // Construct the event date for the current year
        $event_day_month = date('m-d', $event_timestamp);
        $current_year_event_date = strtotime($current_year . '-' . $event_day_month);

        // Determine the correct year to display
        if ($current_timestamp >= $current_year_event_date) {
            // If current date is past or equal to the event date this year, use the next year
            $event_year = $current_year + 1;
        } else {
            // Otherwise, use the current year
            $event_year = $current_year;
        }

        // Replace [nyear] with the calculated event year
        $title = str_replace('[nyear]', $event_year, $title);
    }
}
return $title;

}

add_filter('the_title', 'update_event_year_in_title');
add_filter('pre_get_document_title', 'update_event_year_in_title'); // For meta titles

It hasn’t quite worked yet, but could this be an a good alternative?