Re: [PATCH 08/11] xfs: widen ondisk timestamps to deal with y2038 problem

Mike Fleetwood
2020-08-21T15:31:59Z

On Fri, 21 Aug 2020 at 06:02, griffin tucker
<xfssxsltislti2490@griffintucker.id.au> wrote:
>
> thanks for taking the time to respond to my seemingly stupid questions.
>
> what about interplanetary timestamps? and during transit to the
> moon/planets when time slows?

A little bit of searching provides the answers to your questions, which
are heading off topic.

1. SR and GR time dilation effects are very small [1].
(~0.000027 seconds per day on the ISS [2][3]).
2. It's probably UTC everywhere in the solar system by definition.
(Fixed offset for longitudinal distribution on the surface of a
spinning planet is a separate issue [4]. It's UTC on the ISS [5] and
apparently NASA probes too [6]).
3. Unix time (time_t) works in UTC but with leap seconds ignored [7], so
is not appropriate for anything important in space.
(Imagine if every time a leap second was added GPS was off by most of
the distance to the moon)!

[1] https://en.wikipedia.org/wiki/Time_dilation#Combined_effect_of_velocity_and_gravitational_time_dilation
[2] https://www.businessinsider.com/do-astronauts-age-slower-than-people-on-earth-2015-8?r=US&IR=T
[3] https://spaceflight.nasa.gov/station/crew/exp7/luletters/lu_letter13.html
[4] https://en.wikipedia.org/wiki/Time_zone
[5] https://en.wikipedia.org/wiki/International_Space_Station#Crew_activities
[6] https://solarsystem.nasa.gov/basics/chapter2-3/
[7] https://en.wikipedia.org/wiki/Unix_time