[tz] [IANA #1173666] Time zone change - Yukon Canada

Paul Eggert eggert at cs.ucla.edu
Wed Sep 30 20:37:40 UTC 2020

A lot of what happens will depend on what software is being used. tzdb is used 
by most cell phones and many but not all computers nowadays. If the computers in 
question are not using tzdb, you'll need to talk to whoever's writing the 
software that runs on those computer.

Any copy of tzdb will need to be upgraded to tzdb 2020a (released 2020-04-23) or 
later, and the containing system will typically need to be restarted. Systems 
stuck on older tzdb versions will still operate as if Yukon had not changed its 
timezone rules. This will probably happen on many cell phones, as many are no 
longer supported by their manufacturer or have a user who does not enable 
software updates.

On 9/30/20 12:41 PM, Andrew.Smith at gov.yk.ca wrote:

> Calendar items in Outlook, Google Calendars, Apple Calendar, etc that were entered before a system was assigned to the new Yukon time zone will show as occurring an hour later after Nov. 1, 2020.

This depends on how these applications store time internally. If item times are 
internally stored as UTC or as a fixed offset from UTC or with a timezone like 
"America/Vancouver", you'll see symptoms like what you described. If item times 
are internally stored with timezone "America/Whitehorse" or "America/Dawson", 
they should instead be adjusted as you expected. Problems in this area are 
indeed common. I don't have info about how Outlook etc. operate, but you can 
contact Microsoft, Apple, etc.

> As another example, I have a chicken farmer who is concerned his automated light systems will be off by an hour on Nov. 1. Some people also mentioned traffic light cycles, certainly any appointment booking systems, and my biggest worry is medical devices. The problem will dilute over time as all systems recognize the correct time, but there will be a hangover period by the looks of it.

These are all issues that could happen, yes. Of the problems you mention, 
medical devices and hospital information systems are my biggest concern too.

Although you're right about a hangover period, problems are not necessarily 
limited to a few days or weeks after November 1: they could occur before 
November 1, or many years from now. The latter happened to the Jim Pattison 
Children's Hospital in Saskatoon, whose lab information system crashed roughly 
every two weeks last year due to discrepancies in time zone transitions in the 
1930s and 1940s (!). See:

Eggert P. Hospital lab tests delayed by “Twilight Zone” births. RISKS Digest 
32.16 (2020-07-30). <https://catless.ncl.ac.uk/Risks/32/16#subj9>

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