How to determine time by the position of the planets?

Question

Astronomy

I'm not good at astronomy, but I'm interested. Suppose you need to leave a message to descendants on earth through the millennia. How can they tell the current date so they know exactly how old the message is? Write 2019 from the birth of Christ does not roll, by that time ten ways of reckoning may change. And language can die too. It comes to mind to simply draw the current position of the planets and their satellites, from which they would calculate the date. Isn't it always a unique event? Are the positions cyclical? Or not? Or maybe there are other ways?

Answer 1

Better depict one of the well-visible constellations (for example, Ursa Major) and indicate with great accuracy the angular distances between the stars in it, taking one of the distances as a unit. Also, to simplify identification, it is worth indicating the relative brightness of the stars.