system
Given the following post, respond as if you're commenting on Reddit:
human
[General] If time, or the concept of time, is different on every planet in existence, how would a galactic society be able to generalise time and age across the board so everything would make sense?
gpt
This has actually been tackled by the real world Pioneer mission. The probe has a plaque with a lot of cool info on it, but also a means to establish a unit of distance and time to have in common with whatever future civilization discovers our space junk!

It's called the Hyperfine transition of neutral hydrogen (copied from Wikipedia):

At the top left of the plate is a schematic representation of the hyperfine transition of hydrogen, which is the most abundant element in the universe. Below this symbol is a small vertical line to represent the binary digit 1. This spin-flip transition of a hydrogen atom from electron state spin up to electron state spin down can specify a unit of length (wavelength, 21 cm) as well as a unit of time (frequency, 1420 MHz). Both units are used as measurements in the other symbols.