system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did we come to agree that working 8 hours a day for 5 days a week is the norm?
gpt
That's all thanks to unions - before people started unionizing, there weren't really rules on workers' rights - people could be worked until they collapsed, every day... or maybe with Sunday off for church.

Once industrial workers started unionizing, they had enough pull to work out a deal that's mostly held up ever since: two days of rest, 8 hour days.  The 8 hour days because things could be easily split: 8 hours work, 8 hours sleep, 8 hours for whatever else you want to do.