Something I originally posted in the
"When God said day did he mean an actual 24hour day?" topic:
As I recall, the year was determined to be about 400 days back in the Devonian (approx. 400 million years ago). This was determined by studying daily and annual growth ring paterns in corals.
Anyhow, (365.25 d/y / 400 d/y ) x 24 hr/d = 22 hr/d back in the Devonian.
IF you project that back linearly, that would make the day about 19 hours 1 billion years ago (bya), 14 hours 2 bya, 9 hours 3 bya, 4 hours 4 bya, and 1.5 hours 4.5 bya.
Now, I'll stop, and give everone a chance to say "Who cares".
Moose
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