I want check my iPhone purchas dare
I want to check my iPhone purchase date
Apple Watch
When did I purchase/activate my iphone?
The cynical answer is fro your receipt.
But
Login to https://privacy.apple.com/
Request all data on your AppleID.
After a day or two, you’ll be able to download a fair number of CSVs containing YOUR data as held by Apple.
tip by user Chattanoogan