Re: Predictable Internet Time
Nico Williams <nico@cryptonector.com> Tue, 28 March 2017 17:39 UTC
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Date: Tue, 28 Mar 2017 12:39:18 -0500
From: Nico Williams <nico@cryptonector.com>
To: Stewart Bryant <stewart.bryant@gmail.com>
Cc: ietf@ietf.org
Subject: Re: Predictable Internet Time
Message-ID: <20170328173916.GE7490@localhost>
References: <CAMm+LwgfQJ8aG5wB=d3fRbbeje3J9o7Z4_DCuP8DL88ouDeKzw@mail.gmail.com> <504e2cea0d1668c31486b05fec0a967a4446aefe@webmail.weijax.net> <CAMm+Lwi_jU6gjdtdM6a2n_9_89tUvWBNXxnMtSjTEA++h1D4Ew@mail.gmail.com> <e0a43370-751f-808c-3719-9716f9cd57d1@isi.edu> <alpine.DEB.2.11.1701031348430.7102@grey.csi.cam.ac.uk> <f94415b6-d9f7-0a03-cf5b-ce39c109aa71@isi.edu> <f9429571-b9d5-75d4-9b46-b877a189a7bf@gmail.com>
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On Tue, Jan 03, 2017 at 06:35:03PM +0000, Stewart Bryant wrote: > Yes, the system should use a leap-second-free constant-duration-seconds time > for everything. It is only humans that need the variable jumpy version of > time presented to them, and that is a UI issue. I don't think that's quite right. Unix time is canonically a count of seconds since an epoch and admits no leap seconds. A conversion of Unix time to adjusted (i.e., with leap seconds added) time since the same epoch would be nice, as well as: - conversion from either to broken down time - with seconds count up to 60 when converting from seconds-with-leaps - formatting of dates from either as well as from broken down time - but when converting from seconds-with-leaps the formatted string can show seconds-in-minute values of 60 - whereas when converting from Unix seconds the formatted string can never show seconds-in-minute values of 60 - parsing to broken down time and to seconds-since-epoch types - ignoring leap seconds when converting to Unix time - correctly accounting for all leap seconds prior to that time when converting to seconds-with-leaps-since-epoch It's all about data typing. In POSIX C API terms, we need new functions to deal with seconds-with-leaps-since-epoch, and obviously a lot of prayer because there's no way in C to distinguish one integer type from the other (well, the new type could be wrapped in a struct..). We will have to deal with multiple kinds of time as long as different applications/users need different definitions of time. Astronomers may need corrected time, while bankers may want to ignore leap seconds -- all on the same systems (same OSes, same code libraries). Functionally this is about data typing -- preferably strong data typing. Smearing is a third time representation that also needs conversion to the other types (more opportunity for bugs!); it leaves a bad taste. It may work for some apps though, but all nodes had better smear in exactly the same way -- within your tolerances -- if your app depends on time for synchronization. Nico --
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Toerless Eckert
- Re: Predictable Internet Time Patrik Fältström
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Izaac
- Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time sandy
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Patrik Fältström
- Re: Predictable Internet Time Eliot Lear
- Re: Predictable Internet Time Patrik Fältström
- Re: Predictable Internet Time Eliot Lear
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Cyrus Daboo
- Re: Predictable Internet Time Jared Mauch
- Re: Predictable Internet Time Stewart Bryant
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Cyrus Daboo
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Stewart Bryant
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Stewart Bryant
- Re: Predictable Internet Time Stewart Bryant
- Re: Predictable Internet Time Cyrus Daboo
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Ted Lemon
- Re: Predictable Internet Time Stewart Bryant
- Re: Predictable Internet Time Eliot Lear
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time John C Klensin
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Pete Resnick
- Re: Predictable Internet Time Cyrus Daboo
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Paul Eggert
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Patrik Fältström
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Philip Homburg
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Patrik Fältström
- Re: Predictable Internet Time Eliot Lear
- Re: Predictable Internet Time Harald Alvestrand
- Re: Predictable Internet Time Stewart Bryant
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Leif Johansson
- Re: Predictable Internet Time Eliot Lear
- Re: Predictable Internet Time Leif Johansson
- Re: Predictable Internet Time Phillip Hallam-Baker
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Patrik Fältström
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Michael Breuer
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Tony Finch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Patrik Fältström
- Re: Predictable Internet Time Joe Touch
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Nico Williams
- Re: Predictable Internet Time Harald Alvestrand