Events on the ISS can therefore be considered pretty much real time, even though there is a measurable communications lag. NASA/APL/SwRIOnce you try talking to the outer solar system, the time delays get a little more significant. The light travel delay to New Horizons when it was swinging past Pluto was about four and a half hours, so to ping New Horizons and hear back instantaneously from the craft, you’d be waiting about nine hours. Somewhere around this kind of time delay, we might start to classify things as happening “in the past”, but this is still a time delay on functional human timescales. Not so convenient, especially if something complicated is happening in that time, but also not the worst.

Source: Forbes March 23, 2018 23:15 UTC