I'd say a whole day with no people. It's not like it was a whole year anyway, just 24 hours and I'd be able to keep sanity.
And it doesn't mean I'll necessarily be on my phone the whole day XD
I'll go even further even if it could be just about not seeing people (while people are still around): I would feel claustrophobic if I had to do that on a mondial deserted day.
Who knows, maybe I'll just walk outside without stopping or looking if I have to get aside to let walking people in reversed side pass x )
I'm social, I just feel like when you use your phone for the right things only it can be really useful, like a plus for survival even.
I'll add that "my" devices has been too much taken off back when it wasn't bought by me (years ago), now I'm happy I can let my phone aside while still be able to take it again without depending on someone XD