The Earth spins once, relative to the stars, in 23 hours 56 minutes 4.091 seconds. Aryabhata's opening data-verse (499 CE) counts the Earth's rotations in a cosmic Age — 1,582,237,500, "eastward" — and the division works out to 23 hours 56 minutes 4.10 seconds. One hundredth of a second off, from an era with no clocks beyond water and shadow. And note what he counted: rotations of the Earth, direction included — the spinning-Earth doctrine stated as a table entry, not an argument.