Iphone activation date

Go to Settings->Cellular, then scroll all the way to the bottom. It will tell you when your iPhone was last reset. If you never reset it, then that was the date it was activated.

Head to https://checkcoverage.apple.com and enter your Serial Number. There you will find the date when you warranty ends or ended. This means that your warranty started a year earlier

Unfortunately, you can't. Why do you need it?