I just added code to Lady Heather to calculate time in Terrestrial Time (TT) and Geocentric Terrestrial Time (TCG). The difference is basically the time dilation effect of a time referenced to the center of the earth. Now I'm adding Barycentric Dynamic Time (TDB) which is TT referenced to the center of the solar system... basically another relativistic correction. Does anybody know of an online TT/TCG/TDB clock? I can't seem to find one to check my math. I've also added Mercury/Venus/Pluto time/date... which I've arbitrarily defined as GPS seconds since the J1900 astronomical epoch divided by the orbital period. I decided not to do times for those squishy gas-bag planets. --------------------------- > Hmm, gravitational time dilation it might complicate things ... I suppose it depends on whether your Mars clock is on the surface of Mars, Earth or somewhere else.

Hi …. but what time is it on Titan ???? :) Bob > On Jul 9, 2016, at 6:35 PM, Mark Sims <holrum@hotmail.com> wrote: > > I just added code to Lady Heather to calculate time in Terrestrial Time (TT) and Geocentric Terrestrial Time (TCG). The difference is basically the time dilation effect of a time referenced to the center of the earth. Now I'm adding Barycentric Dynamic Time (TDB) which is TT referenced to the center of the solar system... basically another relativistic correction. > Does anybody know of an online TT/TCG/TDB clock? I can't seem to find one to check my math. > I've also added Mercury/Venus/Pluto time/date... which I've arbitrarily defined as GPS seconds since the J1900 astronomical epoch divided by the orbital period. I decided not to do times for those squishy gas-bag planets. > > --------------------------- >> Hmm, gravitational time dilation it might complicate things ... I > suppose it depends on whether your Mars clock is on the surface of Mars, > Earth or somewhere else. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there.

Calculator here http://astroutils.astronomy.ohio-state.edu/time/hjd2bjd.html Source code to do the conversion also on above site. You should just use their code as it is known correct . BJD (date/time at the center of the solar system) is actually very commonly used . It is the best way to describe the time of an event outside the solar system such as the timing of a variable star. There is a huge amount of published data in BJD. But even within the solar system how do you define when two events are simultaneous? Obviously you need to pick a vantage point where an assumed observer is. The center of mass of the solar system is not a bad choice of vantage point. So when you ask "what is the time on Mars?" Is that what would you see if you had a telescope good enough to read a Martian's wrist watch, or is it what that watch would read if you brought it into your office. Is either of these of much practical use if you had friends living on Mars? Yes, I think the view of the clock through the telescope would be best that way when your friend says he will call you at 8:00am your phone rings when you see his watch reading 8:00am. If you only had a clone of has watch then you'd need a computer to make sense of it. Always when looking at a planet you want to know the observed time (reading watch through telescope) so you can interpret what you see, what is the longitude that is directly facing you. On Sat, Jul 9, 2016 at 3:35 PM, Mark Sims <holrum@hotmail.com> wrote: > I just added code to Lady Heather to calculate time in Terrestrial Time > (TT) and Geocentric Terrestrial Time (TCG). The difference is basically > the time dilation effect of a time referenced to the center of the earth. > Now I'm adding Barycentric Dynamic Time (TDB) which is TT referenced to > the center of the solar system... basically another relativistic correction. > Does anybody know of an online TT/TCG/TDB clock? I can't seem to find one > to check my math. > I've also added Mercury/Venus/Pluto time/date... which I've arbitrarily > defined as GPS seconds since the J1900 astronomical epoch divided by the > orbital period. I decided not to do times for those squishy gas-bag > planets. > > --------------------------- > > Hmm, gravitational time dilation it might complicate things ... I > suppose it depends on whether your Mars clock is on the surface of Mars, > Earth or somewhere else. > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California