system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are time periods (e.g. 50's, 60's, etc.) written with apostrophes?
gpt
They're rightly written with apostrophes, but everyone puts them in the wrong place.  

They're contractions,  - `the 1950s` turns into `the '50s`, just how you would contract `they are` into `they're`