/wp-content/themes/smartbox-theme-1.01/inc/core/options/validation/date.php

<?php
/**
 * Checks for valid date
 *
 * @package Smartbox
 * @subpackage Core
 * @since 1.0
 *
 * @copyright (c) 2013 Oxygenna.com
 * @license http://wiki.envato.com/support/legal-terms/licensing-terms/
 * @version 1.01
 */

/**
 * Validates a date
 *
 * @package Smartbox
 * @since 1.0
 **/
class OxyDate {
    /**
     * Validates the option data
     *
     * @return validated options array
     * @since 1.0
     **/
    function validate( $field, $options, $new_options ) {
        $valid_date = false;
        // get new date value
        $date = $new_options[$field['id']];
        // split up the date into m / d / y
        $parts = explode( '/', $date );
        // do we have m d y ?
        if( count( $parts ) == 3 ) {
            // check if m d y is valid date
            $valid_date = checkdate( $parts[0], $parts[1], $parts[2] );
        }
        // if we have a valid date return new value otherwise report error
        if( $valid_date ) {
            $options[$field['id']] = $date;
        }
        else {
            add_settings_error( $field['name'], $field['id'], $field['name'] . ' - ' . __('Invalid date supplied', THEME_ADMIN_TD), 'error' );
        }
        return $options;
    }
}