Re: Predictable Internet Time

Cyrus Daboo <cyrus@daboo.name> Tue, 03 January 2017 19:54 UTC

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Date: Tue, 03 Jan 2017 14:54:47 -0500
From: Cyrus Daboo <cyrus@daboo.name>
To: Ted Lemon <mellon@fugue.com>
Subject: Re: Predictable Internet Time
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Hi Ted,

--On January 3, 2017 at 1:51:54 PM -0500 Ted Lemon <mellon@fugue.com>; wrote:

>> No that simply does not work. Repeating events or alarms may not involve
>> any UI at all, but the device may need to trigger those at a specific
>> local time - that means time zone information has to be taken into
>> account somewhere. This is a crucial fact of any calendaring and
>> scheduling system that those of us who have been using iCalendar
>> (RFC5545) fully appreciate.
>
> This is true, but any specific local time will always occur at a specific
> universal time, so this isn't actually a problem.

No! That is not true because a future local time is not guaranteed to be at 
a specific universal time because local government can change their time 
zone (or more likely) their daylight savings time transition at any time 
between now and said future time. i.e., you cannot "pre-cache" all the 
local time -> UTC mappings for a future recurring event and then just use 
the UTC values, because the time zone definition may change.

-- 
Cyrus Daboo