timeless

Etymology

time + -less

adj

1. Eternal.
   When Worlds, that count his Circles now, unhing’d, (Fate the loud Signal sounding) headlong rush To timeless Night and Chaos, whence they rose. c. 1743, Edward Young, “Night 2: On Time, Death, and Friendship”, in The Complaint: or, Night-Thoughts on Life, Death, & Immortality
2. Not affected by time; ageless.
3. (obsolete) Done at an improper time; unseasonable; untimely.
   Must I behold thy timeless, cruel death? c. 1591, William Shakespeare, Henry VI, Part 1, act V, scene 4
   The lamp of day is quench’d beneath the deep, And soft approach the balmy hours of sleep: Nor fits it to prolong the heav’nly feast Timeless, indecent, but retire to rest. 1725, Alexander, transl. Pope, The Odyssey of Homer, book 3, London: Bernard Lintot, translation of The Odyssey by Homer, lines 427–430, page 143
4. Not decreasing over time in quality and appeal.
   The cave carvings have a timeless beauty.

noun

1. A gene encoding an essential protein that regulates circadian rhythm, normally written in italics: timeless.