Re: Org mode timestamps on the Moon ;] (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda)

[Ihor Radchenko]

Tom Gillespie  writes:

> Oh boy. In short, I think we can only hope they come up with
> LTC and we already have a syntactic space to say whether
> our reference seconds are TAI/UTC/LTC/MTC/JTC etc. And
> being the privileged squats that we are if the time system is
> left out then it means UTC. The friendly thing to do would be
> to always include the time system code in our timestamps,
> but I don't think those have standard reference codes yet?

I cannot see anything in
https://en.wikipedia.org/wiki/List_of_tz_database_time_zones

So, just UTC. If we want to support more, it will have to be done
manually. 

> I don't think we want to force users to start embedding their gps
> coordinates, their current acceleration, etc. along with their
> timestamp. But it turns out that the unix epoch is only standard
> at 9.8m/s^2. So ... minutes should be ok right?

> Joking aside. Clocks run faster on the moon, slower on the ISS,
> so either clocks are synchronized back to earth seconds, or
> they use some alternate standard reference time.

I am afraid that calculating "real" time inside a given reference system
is impossible now. Time from epoch in Greenwich when you are looking
from inside Greenwich and time from epoch in Greenwich when you are
looking from inside ISS are two different time intervals. And what about
time from epoch in ISS when looking from Greenwich?

And then we also synchronize time with UTC now. But time since epoch in
UTC when looking from UTC and time from epoch in UTC when looking from
different elevation are different times :)

Further, what does it mean to have a meeting scheduled for
<2023-01-30 Mon 14:00 @Europe/Berlin>--<2023-01-30 Mon 20:00 @Asia/Singapore>
What is the reference frame? Europe/Berlin gravitation well?
Asia/Singapore well? Local well?

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at .
Support Org development at ,
or support my work at 

Re: Org mode timestamps on the Moon ; ] (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda)

[Greg Minshall]

Tom,

> The only generalized solution is to record the full location (see
> intro to http://naggum.no/lugm-time.html which I'm surprised hasn't
> been linked in this thread yet, ...

very nice -- thanks for the pointer!

cheers, Greg

Re: Org mode timestamps on the Moon ;] (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda)

[Tom Gillespie]

Oh boy. In short, I think we can only hope they come up with
LTC and we already have a syntactic space to say whether
our reference seconds are TAI/UTC/LTC/MTC/JTC etc. And
being the privileged squats that we are if the time system is
left out then it means UTC. The friendly thing to do would be
to always include the time system code in our timestamps,
but I don't think those have standard reference codes yet?

> would gain about 56 microseconds over 24 hours

And here I was naively hoping to avoid having to deal with
relativistic effects. That would seem to be a pretty serious
issue, but my assumption further down that comment is
hopefully what they will do. Specifically:

> let's just assume that clock synchonization will happen between earth and
> mars so that the unix epoch could be synchronized between the frames

The only generalized solution is to record the full location
(see intro to http://naggum.no/lugm-time.html which I'm surprised
hasn't been linked in this thread yet, but was linked on the same
topic back in 2011 it seems) and let people sort out how to translate
that local time from that reference frame in that particular gravity well.

I don't think we want to force users to start embedding their gps
coordinates, their current acceleration, etc. along with their
timestamp. But it turns out that the unix epoch is only standard
at 9.8m/s^2. So ... minutes should be ok right?

Joking aside. Clocks run faster on the moon, slower on the ISS,
so either clocks are synchronized back to earth seconds, or
they use some alternate standard reference time.

My expectation is that there will be some time keeping standard
that will ensure uniformity and that what we will want to capture
is whose seconds they are using to keep track of time, because
unix epoch on the moon has a different integer value than on
earth, and is likely off by multiple seconds.

I guess as long as the moon can participate in earth NTP it will
be ok? Otherwise I suspect that the NTP network standard for
the celestial body will be what we want to go with/record. I think
that will fit in the opening you have created for this in the syntax.

So instead of UTC it would be LTC (lunar coordinated time).
If you're getting logs from servers on the moon knowing that the
system clock was running on LTC and not UTC will be critical.

Some future engineer: "Leaving earth was a mistake."

Org mode timestamps on the Moon ;] (was: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda)

[Ihor Radchenko]

Tom Gillespie  writes:

> ; given my objective to ensure that org documents can be interpreted
> ; without having to stick stupid things like #+planet: mars in the
> ; header or risk your earthling readers getting incorrect dates --- I
> ; suggest that org switch to storing all dates and times in earth zulu
> ; time ...

https://www.nature.com/articles/d41586-023-00185-z

"The coming decade will see a resurgence in lunar exploration —
including dozens of missions and plans to establish permanent bases on
the Moon. The endeavours pose myriad challenges. Among them is a subtle,
but fundamental, question that metrologists worldwide are working to
answer: what time is it on the Moon?"

...

"It’s not obvious what form a universal lunar time would take. Clocks on
Earth and the Moon naturally tick at different speeds, because of the
differing gravitational fields of the two bodies"

...

"Decisions must be made soon,... If an official lunar time is not
established, space agencies and private companies will come up with
their own solutions" (and Org too?)

...

"Moon missions will also need an official lunar time to cooperate and
communicate, says Hahn. “All this has to trace to one kind of a time
reference, otherwise you have chaos and things do not work together.”"

...

"The Moon’s gravitational pull is weaker than Earth’s, meaning that, to
an observer on Earth, a lunar clock would run faster than an Earth one.
Gramling estimates that a lunar clock would gain about 56 microseconds
over 24 hours" (how will it affect Org's timestamps? should we do
anything about it?)

"...a clock’s speed would also subtly change depending on its position
on the lunar surface, because of the Moon’s rotation" (oh, dear...)

...

“The idea is to produce a Solar System internet,” says Gramling. “And
the first part would be at the Moon.” 

-- 
Ihor Radchenko // yantar92,
Org mode contributor,
Learn more about Org mode at .
Support Org development at ,
or support my work at