More like the precision of ± 0.5 seconds / year, that is to say 15 parts per billion, is that ludicrous. For comparison, time acceleration in geostationary orbi

More like the precision of ± 0.5 seconds / year, that is to say 15 parts per billion, is that ludicrous. For comparison, time acceleration in geostationary orbit due to general relativity is somewhat less than one part per billion. Household tools (other than clocks) rarely go beyond a percent, and if you need a particular quantity you don’t have a ready-made tool for you’ll likely going to be hard-pressed to go beyond ten percent. The more precise you want to be, the more complex and numerous physical phenomena you need to consider become; with a system as involved as the Earth, at some point you get to weather-like chaotic behaviour, so no practical amount of additional precision in input data helps anymore.