For a billion years, Earth may have had 19-hour days. Here's why.

[admin]

Days were once five hours shorter than they are now due to the moon's proximity to Earth, a new study suggests.

For a billion years, Earth may have had 19-hour days. Here's why. : Read more

 

[Broadlands]

"This prolonged period of 19-hour days coincides with a similar slowdown in the rise of oxygen in the atmosphere during the mid-Proterozoic era"

What evidence would there be in the rock record that could support the speculation that there was a "slowdown" in the rise of oxygen over any prolonged length of time? There seem to be a lot of "ifs" in this study.