[wlesieutre]

If I did my math right that's 0.178 seconds per year. As long as everyone's handling time the same way you shouldn't have a problem, but it's enough to be noticeable if someone forgets about it.

I suppose the more noticeable oddness for most people would be that the speed-of-light delay in communications from Earth to Mars varies so much. Around 3 light minutes up to 22 depending on where they are in their orbits.

[Rebelgecko]

That's around what I got from my back of the envelope Math too (well, I got around 300ms/year). Small enough where you can adjust a leap second everyone few years to take care of the drift. Kind of like converting between UTC, TAI, and UT1.

It may need to be compensated for when receiving transmissions between the planets, but I don't know enough about RF to judge how meaningful the difference is. There was a spacecraft (I think Huygens?) that actually had problems with Doppler shift. I think in that case they forgot to take it into account entirely, so it wasn't that they just forgot the relativistic component.