Geodir Custom Field Save example.

        public function add_open_close_fields( $post_type = 'gd_place' ){
            $weekdays = array( 'sunday'    => __( 'Sunday', 'gd_business_hours' ),
                               'monday'    => __( 'Monday', 'gd_business_hours' ),
                               'tuesday'   => __( 'Tuesday', 'gd_business_hours' ),
                               'wednesday' => __( 'Wednesday', 'gd_business_hours' ),
                               'thursday'  => __( 'Thursday', 'gd_business_hours' ),
                               'friday'    => __( 'Friday', 'gd_business_hours' ),
                               'saturday'  => __( 'Saturday', 'gd_business_hours' ), );

            foreach ( $weekdays as $key => $day ){
                self::add_day_open_field( $day, $post_type );
                self::add_day_close_field( $day, $post_type );
            }
        }

        private static function add_day_open_field( $day, $post_type ){
            $field = array( 'listing_type'    => $post_type,
                            'data_type'       => 'TIME',
                            'field_type'      => 'time',
                            'admin_title'     => sprintf( __( '%s opening time', 'gd_business_hours' ), $day ),
                            'admin_desc'      => sprintf( __( 'Time location opens on %s', 'gd_business_hours' ), $day ),
                            'site_title'      => sprintf( __( '%s opening time', 'gd_business_hours' ), $day ),
                            'htmlvar_name'    => strtolower( $day ) . '_open',
                            'default_value'   => '',
                            'option_values'   => '',
                            'is_default'      => '0',
                            'is_admin'        => '1',
                            'show_on_listing' => '0',
                            'show_on_detail'  => '0',
                            'clabels'         => sprintf( __( '%s opening time', 'gd_business_hours' ), $day ), );

            geodir_custom_field_save( $field );
        }

        private static function add_day_close_field( $day, $post_type ){
            $field = array( 'listing_type'    => $post_type,
                            'data_type'       => 'TIME',
                            'field_type'      => 'time',
                            'admin_title'     => sprintf( __( '%s closing time', 'gd_business_hours' ), $day ),
                            'admin_desc'      => sprintf( __( 'Time location closes on %s', 'gd_business_hours' ), $day ),
                            'site_title'      => sprintf( __( '%s closing time', 'gd_business_hours' ), $day ),
                            'htmlvar_name'    => strtolower( $day ) . '_close',
                            'default_value'   => '',
                            'option_values'   => '',
                            'is_default'      => '0',
                            'is_admin'        => '1',
                            'show_on_listing' => '0',
                            'show_on_detail'  => '0',
                            'clabels'         => sprintf( __( '%s closing time', 'gd_business_hours' ), $day ), );

            geodir_custom_field_save( $field );
        }