On 7/10/2026 1:08 PM, Brooks Harris via tz wrote:
There have been very many opinions and reasons discussed about DST for "permanent daylight time" v.s "permanent standard time", from energy, to retail, to school and work times, to sleep patterns, etc.
The one topic I've not seen discussed is the technical difficulties of implementing this "Sunshine Act" proposal. I discussed this with Paul Eggart a couple years ago and he said something to the effect "Whatever we do in this area is going to be a mess".
However TzDb chooses to implement it there seems to be significant difficulties down-stream, such as Unicode CLDR and "Display names" in all the systems. This looks to me like a huge software revision effort with attendant costs and likely confusion and errors.
I hope other experts with more credibility and influence than i have would try to inform the lawmakers of these potential technical difficulties.
-Brooks Harris
Downstream programs should be able to handle "permanent standard time" easier than "permanent daylight time". The US proposal will result in "permanent standard time" with a redefinition of the offsets. -5:00 US E%sT 2027 Nov 6 -4:00 US EST -6:00 US C%sT 2027 Nov 6 -5:00 US CST -7:00 US M%sT 2027 Nov 6 -6:00 US MST -8:00 US P%sT 2027 Nov 6 -7:00 US PST The bad news is the previously mentioned current no DST states. (Such as Arizona ... will they be moved into PST UTC-07 instead of having a separate definition of MST?) And then look to Canada and Mexico. So far (one province - Saskatchewan) their "permanent daylight time" has been recognized as the standard time of the zone to the east. Saskatchewan moved from MST/MDT to CST and that seemed to be accepted. Alberta's move from PST/MDT to CST is modeled after Saskatchewan. In tzdata British Columbia's move from PST/PDT to MST follows what was done for Yukon and eastern British Columbia (with that labeling supported by the National Research Council Canada - at least through 2022). IF the US passes this law then we will have MST in Canada be a different definition than MST in the US. Getting confirmation of when the zones will actually change seems difficult. Zones officially changing "today" (instead of "effective November 1st") adds complexity. Each province and territory wanting to call their zone a different name adds complexity (at least for the downstream). Perhaps Yukon Time, British Columbia Time, Alberta Time, Saskatchewan Time, Manitoba Time would be the best answer to the problem. All we need now is common use. At least the US Law has central control of the zone definitions, both the offsets and names. I see that as good.