International agreements have start times (and a couple of seconds could matter).
Physical things (any future international power supply for example) might depend on it too.
For better or worse, we have to be more charitable with NK than they are with us.
International agreement get violated all the time. good faithfulness is more important than those couple of seconds.
Maybe you do not care, but this stuff is extremely important. Airplanes could crash over a few seconds difference!
Electric grids also make use of DC interconnects that obliviate the need for that synchronization. The contiguous 48 US states have at least 3 separate grids that are interconnected. Roughly east/west/Texas. There may be more, but I'm out of touch with it.
Though I wasn't really thinking about phase sync when I was talking about time and cross-border electricity (indeed, hadn't occurred to me!)
Just scheduling, switching, co-ordination etc. It is likely to me that other international things, both physical and logical) rely at least as much on time being accurate to the second.
ITYM 50Hz