IETF Logo Mail Archive

Re: Predictable Internet Time

Joe Touch <touch@isi.edu> Wed, 04 January 2017 18:11 UTC

Return-Path: <touch@isi.edu>
X-Original-To: ietf@ietfa.amsl.com
Delivered-To: ietf@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id A024112969D for <ietf@ietfa.amsl.com>; Wed, 4 Jan 2017 10:11:58 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -10
X-Spam-Level:
X-Spam-Status: No, score=-10 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, RP_MATCHES_RCVD=-3.1] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id MdgmqK6eH_Es for <ietf@ietfa.amsl.com>; Wed, 4 Jan 2017 10:11:57 -0800 (PST)
Received: from boreas.isi.edu (boreas.isi.edu [128.9.160.161]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id A08081294B6 for <ietf@ietf.org>; Wed, 4 Jan 2017 10:11:57 -0800 (PST)
Received: from [128.9.160.81] (nib.isi.edu [128.9.160.81]) (authenticated bits=0) by boreas.isi.edu (8.13.8/8.13.8) with ESMTP id v04IB4u7029887 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Wed, 4 Jan 2017 10:11:05 -0800 (PST)
Subject: Re: Predictable Internet Time
To: Patrik Fältström <paf@frobbit.se>, Tony Finch <dot@dotat.at>
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> <1483475689.1348946.836323865.09305276@webmail.messagingengine.com> <94226b19-4690-ee8e-526e-04cc54e97b8e@isi.edu> <1483482794.1375510.836410009.6D0F7910@webmail.messagingengine.com> <fef56705-3037-eb92-b804-4aa43326a654@isi.edu> <1483485260.1384841.836469129.669D4C7B@webmail.messagingengine.com> <F3A52DC6-5CF8-4CB5-93A7-78958CBCA725@frobbit.se>
From: Joe Touch <touch@isi.edu>
Message-ID: <5231225a-e0a4-d0ff-2617-8e01cbeed489@isi.edu>
Date: Wed, 04 Jan 2017 10:11:06 -0800
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1
MIME-Version: 1.0
In-Reply-To: <F3A52DC6-5CF8-4CB5-93A7-78958CBCA725@frobbit.se>
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: 8bit
X-ISI-4-43-8-MailScanner: Found to be clean
X-MailScanner-From: touch@isi.edu
Archived-At: <https://mailarchive.ietf.org/arch/msg/ietf/S115oI7rAaKA5KUjJryWQVywxU4>
Cc: Phillip Hallam-Baker <phill@hallambaker.com>, IETF Discussion Mailing List <ietf@ietf.org>
X-BeenThere: ietf@ietf.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: IETF-Discussion <ietf.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ietf>, <mailto:ietf-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/ietf/>
List-Post: <mailto:ietf@ietf.org>
List-Help: <mailto:ietf-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ietf>, <mailto:ietf-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 04 Jan 2017 18:11:58 -0000


On 1/3/2017 11:14 PM, Patrik Fältström wrote:
> Well, if you look at the POSIX definition you see that it is clearly wrong the days when leap second is added:
>
> tm_sec + tm_min*60 + tm_hour*3600 + tm_yday*86400 +
>     (tm_year-70)*31536000 + ((tm_year-69)/4)*86400 -
>     ((tm_year-1)/100)*86400 + ((tm_year+299)/400)*86400
>
>
> 2015-12-31 23:59:58 365th day 61409923198
> 2015-12-31 23:59:59 365th	 day 61409923199
> 2016-01-01 00:00:00   1st day 61409836800
> 2016-01-01 00:00:01   1st day 61409836801
> 									
> 2016-12-31 23:59:59 366th day 61441459199
> 2016-12-31 23:59:60 366th day 61441459200
> 2017-01-01 00:00:00   1st day 61441459200
> 2017-01-01 00:00:01   1st day 61441459201
>
> I.e. the real problem we have is a broken POSIX definition.
It's as correct as it claims to be - it's an approximation.

If anyone cares about a more precise back-calculation of Unix epoch from
UTC, they would definitely need to consult a leap-second file.

Joe

v2.23.0 | Report a Bug | By Email