recurrence-conversion.php

<?php

function convert_recurring_event_meta() {
	global $wpdb;

	// Get meta values
	$event_recurrence_meta = $wpdb->get_results("
		SELECT	post_id, meta_value
		FROM	$wpdb->postmeta
		WHERE	meta_key	= '_EventRecurrence'
	");

	// Update them
	foreach ( $event_recurrence_meta as $event_recurrence_meta_item ) {
		update_event_recurrence_meta( $event_recurrence_meta_item->post_id, $event_recurrence_meta_item->meta_value );
	}

}


/**
 * Helper function to update event meta
 */
function update_event_recurrence_meta( $post_id, $old_recurrence_value ) {

	// Make sure value is unserialised
	$old_recurrence_value = maybe_unserialize( $old_recurrence_value );

	// Skip if the recurrence data is already in the expected form
	if ( count( $old_recurrence_value ) === 3 && ! empty( $old_recurrence_value['rules'] ) ) {
		return;
	}

	$new_value = Tribe__Events__Pro__Recurrence__Meta::get_legacy_recurrence_meta( $post_id, $old_recurrence_value );

  // THIS NEEDS TO BE ADDED TO Tribe__Events__Pro__Recurrence__Meta::get_legacy_recurrence_meta()
	if ( ! isset( $new_value['description'] ) && ! empty( $old_recurrence_value['recurrence-description'] ) ) {
		$new_value['description'] = $old_recurrence_value['recurrence-description'];
	}

	// Update the meta
	update_post_meta( $post_id, '_EventRecurrence', $new_value );
}