without beginning or end; eternal; everlasting.

referring or restricted to no particular time

the timeless beauty of great music.

adjective

abiding , ageless , always , amaranthine , constant , continual , continued , dateless , deathless , endless , enduring , everlasting , forever , illimitable , immemorial , immortal , indefinite , infinite , lasting , never-ending , perennial , permanent , perpetual , persistent , undying , unending , without end , around-the-clock , ceaseless , continuous , eternal , incessant , interminable , nonstop , ongoing , relentless , round-the-clock , unceasing , unfailing , uninterrupted , unremitting , eterne , undated , untimely