Today in existential microdread (small imperfect things that might still keep you up at night):
As the Earth moves around the sun every year, it gets up to 8.3 light-minutes closer to, and then up to 8.3 light-minutes farther from, any particular astronomical event. That’s a 16.6 minute variation over the course of a year! How can we know when astronomical events really occur?!?
So, rather than relative to the Earth, pick a fixed spot, say the Sun, and calculate the time relative to that spot, right?
But no! Because of the motion of the planets, the Sun is not at the center of the mass of the Solar System, so it moves back and forth relative to space, introducing errors of up to 8 seconds.
Real solution: use the Barycentric Julian Date (BJD), which is referenced to the Solar System Barycenter (SSB) , or the center of mass of the Solar System, which doesn’t move relative to space.