Apparently, 86400000 was exact two centuries ago: https://www.theguardian.com/science/2016/dec/07/earths-day-lengthens-by-two-milliseconds-a-century-astronomer

Apparently, 86400000 was exact two centuries ago: https://www.theguardian.com/science/2016/dec/07/earths-day-lengthens-by-two-milliseconds-a-century-astronomers-find https://www.theguardian.com/science/2016/dec/07/earths-day-l...