2 Measuring vitamin D levels is also expensive, costing between $50 and $220 per test in commercial laboratories for patients without insurance. Another challenge is that the level of 25-hydroxy-vitamin D that should be considered normal is unclear.
The closer a planet is to the sun, the shorter the time to complete one revolution is. Mercury, for example, has an orbital period of 88 days while it takes Jupiter about 11.86 years. The period of the Earth's orbit is usually thought to be 365 days as calendars show. However when averaged it is actually about 365.25 days, which requires an extra day on the calendar every four years (causing a leap year). Contradictions within orbit times are probably caused by the ages of the sources.
Hadean Eon [4500 Myr - 4000 Myr ] The age of the Earth is projected to be about 4500 Myr from radiometric dating of the oldest rocks and meteorites. There is evidence of a time of intense bombardment of the Earth in the time period from about 4100 to 3800 Myr in what is called the late heavy bombardment.