From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,7dadb26e573572d X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2003-12-09 08:00:08 PST Path: archiver1.google.com!news2.google.com!fu-berlin.de!uni-berlin.de!82-43-33-75.cable.ubr01.croy.blueyonder.co.UK!not-for-mail From: Nick Roberts Newsgroups: comp.lang.ada Subject: Re: ada calendar Date: Tue, 09 Dec 2003 15:59:58 +0000 Message-ID: References: NNTP-Posting-Host: 82-43-33-75.cable.ubr01.croy.blueyonder.co.uk (82.43.33.75) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Trace: news.uni-berlin.de 1070985606 76501848 82.43.33.75 ([25716]) User-Agent: Mozilla/5.0 (Windows; U; Win95; en-GB; rv:1.5) Gecko/20031007 X-Accept-Language: en-gb, en, en-us In-Reply-To: Xref: archiver1.google.com comp.lang.ada:3278 Date: 2003-12-09T15:59:58+00:00 List-Id: tmoran@acm.org wrote: >>Will this revision include definitions based on precise >>description of movements of the Earth ? The rotation > > My understanding is that Ada.Calendar is basically a wall clock - it > can be reset by the operator for Daylight Savings, leap seconds, clock > skew, or whatever. It's the right thing to use for printing a date & time > on a report, for instance. Ada.Real_Time has a monotonic clock so it's > generally the right thing for elapsed time. Inserting a leap second for > instance would cause the clock to run backwards one second, which would be > illegal for Ada.Real_Time.Clock, but perfectly OK for Ada.Calendar.Clock I think this is quite correct. The proposal does include minimal (very minimal) time zone functionality, but I suspect this might be removed by the ARG (or WG9), as being too horrible to contemplate. [For one thing, it is only the rather obscure UT0 time system that is actually based on movements of the Earth; UT1 corrects it for 'wobble'. UTC is based on atomic clocks, and is corrected in steps of precisely 1 second every now and then to bring it within 0.9 s of UT1. As for the all the different time zones in use around the world, that is a deep mire where only the very foolish or the very brave (or those who enjoy maintaining huge databases) dare to tread.] -- Nick Roberts