From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mp12.migadu.com ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by ms5.migadu.com with LMTPS id UAemL26gxWNwQgEAbAwnHQ (envelope-from ) for ; Mon, 16 Jan 2023 20:07:26 +0100 Received: from aspmx1.migadu.com ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by mp12.migadu.com with LMTPS id QOGQL26gxWO4DwAAauVa8A (envelope-from ) for ; Mon, 16 Jan 2023 20:07:26 +0100 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 294E62DD58 for ; Mon, 16 Jan 2023 20:07:26 +0100 (CET) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pHUof-0008L0-JR; Mon, 16 Jan 2023 14:06:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pHUod-0008Ke-Rg for emacs-orgmode@gnu.org; Mon, 16 Jan 2023 14:06:43 -0500 Received: from mout02.posteo.de ([185.67.36.66]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pHUoa-0005oW-O1 for emacs-orgmode@gnu.org; Mon, 16 Jan 2023 14:06:43 -0500 Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 73803240223 for ; Mon, 16 Jan 2023 20:06:38 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1673895998; bh=UI6ghGGvFf+hYgJJ2sqaC7lWnFHBS7f/tiPz1ioO7Xo=; h=From:To:Cc:Subject:Date:From; b=eAUqEdDpB5rsenfvb2ooaZM0453s2GiQlz7jS3t/IJVk69aYtnkBan4+BfnMMqsNj DJ2fEodcwoSis/kbFB6MJ94QGA8dWtSrmIW6z04VHveMv20X10P005u4W3GVh8jbMZ utD+WX0pmhPJzyM0ZkbO7TQLPuJqBK6hW8Mo1d6KMI0fvsonKGbL5h5jytt0SfTTvj vfQ6c9MF5cO0w6luYUMQYmxcWIXcotLNjF5fmSodrX2Eu1ZZGjU/dy7pYP6YqR7SrC rX68DzVzMvbHgETzilT0tL1uCnCh9QAWJpICxJUE5Xy3c9jUOeNxM7SNnrUrMWPV3y xj9fiVDUMXGxw== Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4NwhMd4pNwz9rxG; Mon, 16 Jan 2023 20:06:37 +0100 (CET) From: Ihor Radchenko To: Daryl Manning Cc: emacs-orgmode@gnu.org Subject: Re: [FEATURE REQUEST] Timezone support in org-mode datestamps and org-agenda In-Reply-To: References: <86zgamtv6o.fsf@gmail.com> <87tu0t1i0c.fsf@localhost> <63c2aa9e.170a0220.3bb49.9ef4@mx.google.com> <87pmbhz1x6.fsf@localhost> <87wn5mlo7f.fsf@localhost> <87pmbelnd0.fsf@localhost> Date: Mon, 16 Jan 2023 19:07:09 +0000 Message-ID: <87fscajo2q.fsf@localhost> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=185.67.36.66; envelope-from=yantar92@posteo.net; helo=mout02.posteo.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H2=-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: 2.1.29 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-bounces+larch=yhetil.org@gnu.org X-Migadu-Country: US X-Migadu-Flow: FLOW_IN ARC-Authentication-Results: i=1; aspmx1.migadu.com; dkim=pass header.d=posteo.net header.s=2017 header.b=eAUqEdDp; spf=pass (aspmx1.migadu.com: domain of "emacs-orgmode-bounces+larch=yhetil.org@gnu.org" designates 209.51.188.17 as permitted sender) smtp.mailfrom="emacs-orgmode-bounces+larch=yhetil.org@gnu.org"; dmarc=pass (policy=none) header.from=posteo.net ARC-Seal: i=1; s=key1; d=yhetil.org; t=1673896046; a=rsa-sha256; cv=none; b=o66fB+mSHRvf9QqdD9psiqK7w9TvOxAMSHDwNl1C3KWAu8WgodeQoPvki+ZL1fPXaeH/xQ UKE+w1lSx49XOsf2jW8EgY8IqEtXGqBZdBT7onx69RR+2FuYzNdRM+iVX4bnqexT+Jdfst R4BToC3JM3YhOT40FtnrEaQT0apU1U2yABmBukEpS2dhbajTzHaVmTLrrQGLpFewThvVDr 6r9t1YpNwauBo0ic0PGVCYJcdOELR7GSSFhgAmpjAV6cMJoO1N4INqBkJoQ6t3EDJAe9Qm lM4+iwuR/cp+cczecTUd8qFFlVr0Xv2cYFudmDbGep2FFMkEyXc9IGIgkLjJXw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=yhetil.org; s=key1; t=1673896046; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references:list-id:list-help:list-unsubscribe: list-subscribe:list-post:dkim-signature; bh=v2a17SKuNQK49VSWbvT+TMsswMRzysw2waTlLkm29Ms=; b=q/bXsiB5TKCQDsrVZ/W88enGM2Af5eSoW5HTF8xwKCxuWNigzhgkVqphDZWKs7AKGFOygt yRdruGf4VETm9rRwt6IS8JGllqqeVQ4MhrT99SxY+EInEdv1q46b+mzTosyymbg0RV+Qpl FibjiCgG0wRxJBkiHz4FuisheHTgb0X8U6mfWGa6iSZ4IwbJxXwT2XTHy/be/7LIC/J4GV SoToaYos53TyXEZWIPWkwb4rBM3BPz+cMzN2TtvCdsrih6pViC6OGwhaM8DNSsm2NqBoEg WCxKVqqrHee6GQC0p3EV5hZhRx3ghEi9ovpG3MQhJ9Mkm9/uFuGR/d7EK/6jKA== X-Migadu-Queue-Id: 294E62DD58 X-Migadu-Scanner: scn0.migadu.com Authentication-Results: aspmx1.migadu.com; dkim=pass header.d=posteo.net header.s=2017 header.b=eAUqEdDp; spf=pass (aspmx1.migadu.com: domain of "emacs-orgmode-bounces+larch=yhetil.org@gnu.org" designates 209.51.188.17 as permitted sender) smtp.mailfrom="emacs-orgmode-bounces+larch=yhetil.org@gnu.org"; dmarc=pass (policy=none) header.from=posteo.net X-Migadu-Spam-Score: -9.87 X-Spam-Score: -9.87 X-TUID: l7BooR8u6noL Daryl Manning writes: > I'd just be excited to have us run through the basic use cases and then see > some more "tricky" ones. I imagine there are things we'd just have to > say... too tricky for (eg. flight takes off in one TZ and range allows it > to land in timezone... stuff like that might be tricky.). https://www.youtube.com/watch?v=-5wpm-gesOY gives various examples. To summarize: 1. Time (YYYY-MM-DD HH:MM) not continuous and may change arbitrarily at certain times a year or in future or in the past: - DST transitions are not stable and change from year to year according to strange rules that may involve Julian dates or counting weekdays - DST transition rules may change over time - The new year day itself is not necessarily fixed (England - Julian/Gregorian transitions happened at different times in different countries 2. There might be arbitrary time gaps due to time transition, including time overlaps with the same time of the day happening multiple time a day: - One hour back during DST transition (northern and southern hemispheres do the transitions in opposite directions) - Multiple days skipped (Samoa skips a whole day during DST transition) - Great Britain used 2 hours DST offset during WWII - Julian/Gregorian calendar transitions in the past 3. We cannot assume that the same geographical area has fixed time zone even at given point of time: - Palestinian/Israeli people follow different time zones in the contested territories 4. Great Britain had new year on March 25 until 16th century (March 24, 1000 -> (+1 day) March 25, 1001) 5. Leap seconds! 23:59:59 -> 23:59:60 -> 00:00:00, according to astronomical Earth observations > So, is the TS syntax you've described accepted and canonical now with > org-mode? We are still discussing it. -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at . Support Org development at , or support my work at