Checks themes versions only after a duration of time.

This is for performance reasons to make sure that on the theme version checker is not run on every page load.

File: wp-includes/update.php. View all references

function _maybe_update_themes() {
	$current = get_site_transient( 'update_themes' );

	if ( isset( $current->last_checked )
		&& 12 * HOUR_IN_SECONDS > ( time() - $current->last_checked )
	) {
		return;
	}

	wp_update_themes();
}