https://www.newscientist.com/article/mg24732960-900-inside-the-incredibly-slow-race-to-reinvent-time/
Do we need to recalibrate clocks with the latest scientific timepiece? It seems tyrannical to have to hitch our wagon train to such an exclusive and inaccessible instrument. In any case, Einstein’s a priori assumption that the speed of light is constant prevents that being verified by measurement because no independent clock is available. The notion of universal time seems practically useful but epistemologically unsound. Updating it obfuscates the main issue which is that humans have become obsessed with regulating their affairs by timepieces instead of tuning into personal experience of time. I have written a fiction novel Time is Gold which explores time in athletic endurance.
http://www.martinknox.com

Time measurement is assumed to be precise.