When does the warranty start for my iPad?
I heard it's when you "register" it with Apple, i.e.: when you start using it and sign in with your Apple ID.
Am I right?
Warranty Period is defined as
a period of ONE (1) YEAR from the date of original retail purchase by the end-user purchaser
which is purchase date, not first use date.
https://www.apple.com/uk/legal/warranty/products/uk-ireland-universal-warranty.html
Check your own country warranty in case it’s different.