What are some options for a timestamp,
like a pattern of sunpots, not a human related thing like dedicated timestamp authorities?
(Even chatgpt won't give me any idea, just forces the use of authorities, even after a long converstation said to make photos of newspaper, after my example was the daily titles of 20 bigest journals.
👤 robga Accepted Answer ✓
On the macro scale, would measuring sidereal time or pulsars meet your requirement?
On the micro scale, atomic clocks?