function bp_update_user_last_activity( $user_id = 0, $time = '' ) {

	// Fall back on current user.
	if ( empty( $user_id ) ) {
		$user_id = bp_loggedin_user_id();
	}

	// Bail if the user id is 0, as there's nothing to update.
	if ( empty( $user_id ) ) {
		return false;
	}

	// Fall back on current time.
	if ( empty( $time ) ) {
		$time = bp_core_current_time();
	}

	// As of BuddyPress 2.0, last_activity is no longer stored in usermeta.
	// However, we mirror it there for backward compatibility. Do not use!
	// Remove our warning and re-add.
	remove_filter( 'update_user_metadata', '_bp_update_user_meta_last_activity_warning', 10 );
	remove_filter( 'get_user_metadata', '_bp_get_user_meta_last_activity_warning', 10 );
	bp_update_user_meta( $user_id, 'last_activity', $time );
	add_filter( 'update_user_metadata', '_bp_update_user_meta_last_activity_warning', 10, 4 );
	add_filter( 'get_user_metadata', '_bp_get_user_meta_last_activity_warning', 10, 4 );

	return BP_Core_User::update_last_activity( $user_id, $time );
}