This is a watch ad from 1972:
(https://i.ibb.co/CpQF6h11/nipponese.jpg)
The reference to the Expo '70 Atomic Clock intrigued me so I asked an AI: what's the most accurate clock technology now?
It turns out that optical lattice clocks, a modern form of atomic clock, are accurate to less than half a second over the entire age of the universe (from big bang to present day), which is 13.8 billion years - or a second every 31.72 billion years.
https://phys.org/news/2024-07-optical-lattice-clock-based-strontium.html
Published on Monday:
https://www.nist.gov/news-events/news/2025/07/nist-ion-clock-sets-new-record-most-accurate-clock-world
.. Slightly more accurate than an optical lattice clock. Would gain or lose about 1/3 of a second over the same 13.8 billion years instead of half a second. Less practical but incredibly clever - uses "quantum logic operations" and requires extreme environmental isolation.