I'm often trying to peg the age of a show or movie by the cars or tech shown on screen.
The clearest demarcation I've noticed is 2008.
Smart phone? after 2008. Flip phone? Most likely before. No Mobile? Pre 1990s I guess...?
I don't know the exact dates, but there is a subset of smart phones too. Where you see product placement of a Windows phone that is a relatively small window of time.