There is no reason all phones would have the same time. I know some US phones sync the time with the carrier, which is a great function but not seen in the rest

There is no reason all phones would have the same time. I know some US phones sync the time with the carrier, which is a great function but not seen in the rest of the world. You could use bluetooth, but then you have to switch it on. You could use the camera to pick up the phones behind you somehow, but that would not always work.