At https://tallbloke.wordpress.com/2020/03/10/ancient-shell-shows-days-were… … ancient mollusc shell shows days were half hour shorter 70 million years ago- slap bang in the end of Cretaceous impact event (depending on how you interpret the sedimentary layers laid down as a result of the impact event). The date of the mollusc shell is the intriguing point as it would have lived prior to the Chicxulub asteroid strike (however you wish to date those sedimentary layers, uniformitarian or catastrophist). Earth turned faster in the dinosaur age than it does today. A day lasted 23 and one half hours rather than 24, and rotated 372 times a year rather than 365.
The mollujsc was in fact a clam shell – of an extinct species. It grew fast enough to lay down daily growth rings. The study used lasert to sample very small slivers of shell in order to count the rings more accurately than human eyes with microscopes.