On the 7th day God rest. I know a friend of mine probably has an answer, but why did God need a day of rest? He is God after all. And if our day of rest is Sunday, why is it the first day on the calendar? Different cultures and religions have it different though.

I know the Romans and religions have a lot to do with it. And does it really matter?

https://thetylt.com/culture/sunday-calendar