If you got into a time machine and went back to 1821, what would your cellphone say when you got there?

It would probably show the last date it received and its internal clock and calendar would continue to function while the battery lasted. All the in-phone functions would continue to work but there would be no external connections so no service.  There would be no electricity supply with which to recharge the phone's battery ... so nothing to power the time machine to get you back.

How would the phone know that it was in the last ? It's not like 1821's Verizon equivalent will be able to synch up it's clock function.

Dunno. I don't carry a cellphone all the time.

Ok, if you want wayyy up into the mountains where there is no signal, it would say the same thing.

Siri, would tell me there is no service

Absolut Ning nothing.

It would say “What the WHAT?” and then die.  

I would be able to accees internal memory only, until the battery went dead.

Nothing.  It will be dead.  No coverage in 1821....in fact no phones in those years.

Peace.

"no service available"

............no service