[tz] Yukon to move to year-round PDT

[Chris Walton]

>>> I agree with Michael D.
>>> 
>>> There are four existing zones that are already on permanent UTC-7:
>>> 	America/Dawson_Creek
>>> 	America/Creston
>>> 	America/Fort_Nelson
>>> 	America/Phoenix
>>> None of these zones makes use the DST bit.  The time zone is displayed year round as MST instead of PDT.  I don't think anybody complains about it.
>>> 
>>> I don't see any compelling reason to treat the two Yukon zones (America/Whitehorse & America/Dawson) any differently than the four existing UTC-7 zones.
>>>  
>>Historic timestamps?
>Historic timestamps and their time zone abbreviations do not change.  Nobody is suggesting that they should be changed.
>e.g. America/Dawson already supports all the historical time zone abbreviations that have been used in Yukon Territory since 1900:
>      PDT, PST, YDDT, YDT, YPT, YST , & YWT.
>The proposed change would force all dates that occur after March 14/2021 to have an MST time zone abbreviation.
>All dates that occur before March 14/2021 would continue to be displayed with the correct historical time zone abbreviations.
Correction: the change takes place this upcoming weekend (March 8/2020).  It is not March 14/2021 as I indicated in my previous e-mail.
-chris