[ianburrell]

Space travel will be relatively easy since requires computers. Everyone will keep track of their local clock in seconds. Then they will calculate clock for places they care about, eg Earth-time, since those are pretty predictable. Relativistic corrections will be pretty minor.

My guess is that planets will keep local day-year. Mars is close enough to Earth that throwing in extra 37 min might make sense. OTOH, most planets and moon might use Earth calendar because local day cycle is too far off human internal clocks.

They will calculate time for other places, but will be less important than time zones since every communication will have light speed lag. No video calls, but lots of email.