It's a great way to test various limits. When you think about this even more, it's a little mind-bending, as we're trying to impose a global clock ("who is the most up to date") on a system that inherently doesn't have a global clock. When we scale time down to nanoseconds, this affects us in the real world of today: a light-nanosecond is not very far.

Which of these to use depends on the result you want. Note that by the time you get the answer, it may be incorrect (out of date). There is no way to fix this locally. Using some ESP,2 imagine the remote you're contacting is in orbit around Saturn. It takes light about 8 minutes to travel from the sun to Earth, and about 80 to travel from the sun to Saturn, so depending on where we are orbitally, they're 72 to 88 minutes away. Any answer you get back from them will necessarily be over an hour out of date.

Exaggeration of System Parameters