From: Mike Fleetwood <mike.fleetwood@googlemail.com>
To: griffin tucker <xfssxsltislti2490@griffintucker.id.au>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>, linux-xfs@vger.kernel.org
Subject: Re: [PATCH 08/11] xfs: widen ondisk timestamps to deal with y2038 problem
Date: Fri, 21 Aug 2020 16:31:44 +0100 [thread overview]
Message-ID: <CAMU1PDg0JGtJ9ggj1sZXbw8FquQ_RJSOc1otNQ2tqbdfzCt7ZQ@mail.gmail.com> (raw)
In-Reply-To: <CAH3XsHF=bPBvogcWTRaK8XDFF2zu5Q5Mc++FUJYb8eHY9u_zqQ@mail.gmail.com>
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
next prev parent reply other threads:[~2020-08-21 15:31 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-17 22:56 [PATCH v2 00/11] xfs: widen timestamps to deal with y2038 Darrick J. Wong
2020-08-17 22:56 ` [PATCH 01/11] xfs: explicitly define inode timestamp range Darrick J. Wong
2020-08-18 6:25 ` Amir Goldstein
2020-08-17 22:57 ` [PATCH 02/11] xfs: refactor quota expiration timer modification Darrick J. Wong
2020-08-18 6:48 ` Amir Goldstein
2020-08-18 15:40 ` Darrick J. Wong
2020-08-17 22:57 ` [PATCH 03/11] xfs: refactor default quota grace period setting code Darrick J. Wong
2020-08-18 10:46 ` Amir Goldstein
2020-08-17 22:57 ` [PATCH 04/11] xfs: remove xfs_timestamp_t Darrick J. Wong
2020-08-18 10:50 ` Amir Goldstein
2020-08-17 22:57 ` [PATCH 05/11] xfs: move xfs_log_dinode_to_disk to the log code Darrick J. Wong
2020-08-18 10:51 ` Amir Goldstein
2020-08-17 22:57 ` [PATCH 06/11] xfs: refactor inode timestamp coding Darrick J. Wong
2020-08-18 11:20 ` Amir Goldstein
2020-08-18 15:42 ` Darrick J. Wong
2020-08-17 22:57 ` [PATCH 07/11] xfs: convert struct xfs_timestamp to union Darrick J. Wong
2020-08-18 11:24 ` Amir Goldstein
2020-08-17 22:57 ` [PATCH 08/11] xfs: widen ondisk timestamps to deal with y2038 problem Darrick J. Wong
2020-08-18 12:00 ` Amir Goldstein
2020-08-18 12:53 ` Amir Goldstein
2020-08-18 15:53 ` Darrick J. Wong
2020-08-18 20:52 ` Darrick J. Wong
2020-08-18 15:44 ` Darrick J. Wong
2020-08-18 23:35 ` Dave Chinner
2020-08-19 21:43 ` Darrick J. Wong
2020-08-19 23:58 ` Dave Chinner
2020-08-20 0:01 ` Darrick J. Wong
2020-08-20 4:42 ` griffin tucker
2020-08-20 16:23 ` Darrick J. Wong
2020-08-21 5:02 ` griffin tucker
2020-08-21 15:31 ` Mike Fleetwood [this message]
2020-08-20 5:11 ` Amir Goldstein
2020-08-20 22:47 ` Dave Chinner
2020-08-17 22:57 ` [PATCH 09/11] xfs: refactor quota timestamp coding Darrick J. Wong
2020-08-18 12:25 ` Amir Goldstein
2020-08-17 22:57 ` [PATCH 10/11] xfs: enable bigtime for quota timers Darrick J. Wong
2020-08-18 13:58 ` Amir Goldstein
2020-08-18 15:59 ` Darrick J. Wong
2020-08-17 22:57 ` [PATCH 11/11] xfs: enable big timestamps Darrick J. Wong
2020-08-18 14:04 ` Amir Goldstein
2020-08-18 23:01 ` [PATCH v2 00/11] xfs: widen timestamps to deal with y2038 Dave Chinner
2020-08-18 23:10 ` Darrick J. Wong
2020-08-18 23:41 ` Dave Chinner
2020-08-21 2:11 [PATCH v3 " Darrick J. Wong
2020-08-21 2:12 ` [PATCH 08/11] xfs: widen ondisk timestamps to deal with y2038 problem Darrick J. Wong
2020-08-22 7:33 ` Christoph Hellwig
2020-08-24 2:43 ` Darrick J. Wong
2020-08-25 0:39 ` Darrick J. Wong
2020-08-24 1:25 ` Dave Chinner
2020-08-24 3:13 ` Darrick J. Wong
2020-08-24 6:15 ` Dave Chinner
2020-08-24 16:24 ` Darrick J. Wong
2020-08-24 21:13 ` Darrick J. Wong
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