From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mp1 ([2001:41d0:2:bcc0::]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) by ms0.migadu.com with LMTPS id GP/QJpK6Z2CNFwAAgWs5BA (envelope-from ) for ; Sat, 03 Apr 2021 02:45:06 +0200 Received: from aspmx1.migadu.com ([2001:41d0:2:bcc0::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by mp1 with LMTPS id OECPIJK6Z2BNcQAAbx9fmQ (envelope-from ) for ; Sat, 03 Apr 2021 00:45:06 +0000 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by aspmx1.migadu.com (Postfix) with ESMTPS id DA33ECABC for ; Sat, 3 Apr 2021 02:45:05 +0200 (CEST) Received: from localhost ([::1]:47910 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lSUPQ-00019u-J2 for larch@yhetil.org; Fri, 02 Apr 2021 20:45:04 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33492) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lSUOL-00019a-Bw for emacs-orgmode@gnu.org; Fri, 02 Apr 2021 20:43:57 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:34393) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lSUOJ-00087K-G3 for emacs-orgmode@gnu.org; Fri, 02 Apr 2021 20:43:57 -0400 X-Originating-IP: 61.149.237.132 Received: from [192.168.1.31] (unknown [61.149.237.132]) (Authenticated sender: shironeko@tesaguri.club) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id 2517560004; Sat, 3 Apr 2021 00:43:50 +0000 (UTC) Message-ID: <1fdca9a5e7e91136d0c4b8d6a38d2ca3dbc0f7d4.camel@tesaguri.club> Subject: Re: Idea for handling timezones From: Shironeko To: Tim Cross , emacs-orgmode@gnu.org In-Reply-To: <87blawgrj3.fsf@gmail.com> References: <87blawgrj3.fsf@gmail.com> Content-Type: text/plain; charset="UTF-8" Date: Sat, 03 Apr 2021 08:43:47 +0800 MIME-Version: 1.0 User-Agent: Evolution 3.38.4 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=217.70.183.195; envelope-from=shironeko@tesaguri.club; helo=relay3-d.mail.gandi.net X-Spam_score_int: -25 X-Spam_score: -2.6 X-Spam_bar: -- X-Spam_report: (-2.6 / 5.0 requ) BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-orgmode@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "General discussions about Org-mode." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-orgmode-bounces+larch=yhetil.org@gnu.org Sender: "Emacs-orgmode" X-Migadu-Flow: FLOW_IN ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=yhetil.org; s=key1; t=1617410706; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:list-id:list-help: list-unsubscribe:list-subscribe:list-post; bh=EQ7RTH8lStF+p9By7r8dNE43xjqEW/JoPIxU1Q9Beq0=; b=s3mvGNqfDlO0D60c6BLKdxTG/xWAMagzJyBGflTh5u7H17IJI7d0wj5WKAUad4YyAlsIUv O/oVZD0Qd+tDWK2b94VZLOhuMxWp48tZnYZmLL0g01HdxSTBnBK5hsvhEjf1L1ZhmdtuSv t6n0/g4iQR5F0M3PcrIMS3uc+Fb23d23cnCHAl52/wmHt9Yv4szf2zH1+UXycZVTFT4BJg JNbjMC5c4jM7fdDidzHMgEa3OX07GI9xOB2k3GduVODJjFHJokrwMLkXpQ+1RBiThhlRcY YdmrAkCWanUAtmw55mSUBNVyKHxd90HT8+ge/V1CR2HGGgJWQ3zW16vgAnxxZg== ARC-Seal: i=1; s=key1; d=yhetil.org; t=1617410706; a=rsa-sha256; cv=none; b=Cbq0Z2kl9d5AwuFd1P0H6RutSs7gYp6Z5GsEAuihhRlHRUBUTo+4qqKc/kOTvZ7A+xI+PE z4FdEtVbt2wR4Sz57mZiFzytr3EY4BNmSVAi3/urkglggiRGyQoV6PfCQ8O/N4zm3XGfnI OlabJ+JMjCBiHiTvR6YLAPrFsnBY6NNigwYtXROQUQZstocyiG/8MMaQQqTFiLr6OeYhbz oCB3WjIQG3pGExc8ZsCvRwI5/aOG3w0boyhPgLxFfqN/srUkWCkyjoDcdM2TBlmIPvcWoW 7gb2VWGcsDJWWCopDxdJlgQ1KIDC/ws0g+k/9xZV01ojXwBncpjGizG6Axs1Sw== ARC-Authentication-Results: i=1; aspmx1.migadu.com; dkim=none; dmarc=none; spf=pass (aspmx1.migadu.com: domain of emacs-orgmode-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=emacs-orgmode-bounces@gnu.org X-Migadu-Spam-Score: -2.43 Authentication-Results: aspmx1.migadu.com; dkim=none; dmarc=none; spf=pass (aspmx1.migadu.com: domain of emacs-orgmode-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=emacs-orgmode-bounces@gnu.org X-Migadu-Queue-Id: DA33ECABC X-Spam-Score: -2.43 X-Migadu-Scanner: scn0.migadu.com X-TUID: 2PC9qrQvEDHg On Sat, 2021-04-03 at 10:37 +1100, Tim Cross wrote: > > 1. Timzone alone is not sufficient. Offsets from UTC change due to > daylight savings times etc. > > 2. You can easily have timestamps from different timezones in the same > org file > > 3. Storing timestamps in local time is problematic because of the > inherent ambiguity this can have (again, due to daylight savings times > and what occurs at the 'cut over' time). > > 4. Sometimes, you may want the timestamp to reflect the date/time as it > was when recorded and don't want it to 'change' because your now viewing > it in a different timezone etc. 1 and 3 is addressed by the use of tz database, it makes sure the timezone conversion is lossless. 2 and 4 is really not the target for this proposal, this feature is completely optional and this is really meant to solve the "I want to see when I need to get my tasks done" which is a particular headache when there is timezone involved. > Personally, I think timestamp 'storage' and timestamp 'display' need to > be treated separately. I also think all relevant information (timezone, > offset) need to be stored with the timestamp. I also think the > fundamental base timestamp should be stored as UTC, allowing all time > calculations to be consistent (free of daylight savings time changes). > The user can then manage how the value is displayed by setting timezone > and offsets as appropriate (with perhaps the default being the local > system settings or whatever offset/tz was stored with the timestamp > itself). > > It is very difficult to predict or understand all the use cases for > timestamps. Therefore, any scheme must be extremely flexible. Experience > has taught me that one critical component is that at the lowest level, > many problems are avoided if the value is in UTC. Problem is, UTC is not > terribly human friendly. Luckily, this can largely be automated for many > common use cases. Unfortunately, it does also mean that if you are > someone who frequently moves between many timezones, your situation will > be more complicated. > > ne of the most frustrating parts of working with timestamps is daylight > saving times. This causes complications at so many levels. In > particular, I hate the fact change over dates often change and more > often than not, those changes are based around politics and at the whim > of politicians, which makes programatic handling more complex than it > needs to be. > yes, this is why I want to avoid changing the timestamp itself, since that will never lead to working solutions soon. Regards, shiro