function bp_core_get_last_activity( $last_activity_date = '', $string = '' ) {

	// Setup a default string if none was passed.
	$string = empty( $string )
		? '%s'     // Gettext placeholder.
		: $string;

	// Use the string if a last activity date was passed.
	$last_active = empty( $last_activity_date )
		? __( 'Not recently active', 'buddypress' )
		: sprintf( $string, bp_core_time_since( $last_activity_date ) );

	/**
	 * Filters last activity string based on time since date given.
	 *
	 * @since 1.2.0
	 *
	 * @param string $last_active        Last activity string based on time since date given.
	 * @param string $last_activity_date The date of last activity.
	 * @param string $string             A sprintf()-able statement of the form 'active %s'.
	 */
	return apply_filters( 'bp_core_get_last_activity', $last_active, $last_activity_date, $string );
}