[tz] Tzdb and the Sunshine Protection Act

Brooks Harris brooks at edlmax.com
Fri Mar 3 16:12:20 UTC 2023

On 2023-03-02 5:44 PM, Paul Eggert wrote:
> On 3/2/23 14:22, Brooks Harris via tz wrote:
>> How will tzdb manage this?
> Traditionally we've treated "permanent daylight saving" as standard 
> time, and I'd rather continue this tradition than make an exception 
> for the US. That is, tm_isdst would be 0. (Most people don't care 
> about the tm_isdst flag, but POSIX and C standard nerds do.)
> Whether the adjusted time in (say) New York would be abbreviated "EST" 
> or "AST" or "EDT" is up to common practice. We could use the 
> abbreviation "-04" until common practice settles down. If common 
> practice becomes "ET" we couldn't use that, unfortunately, as POSIX 
> requires at least three characters. At some point "EST" might become 
> the best of the alternatives.
> My biggest worry is the set of backward compatibility zones EST5EDT, 
> CST6CDT, MST7MDT, PST8PDT as their continued use would lead to so much 
> confusion that they'd be more trouble than they're worth. Presumably 
> we would retire them by moving them to "backzone". "EST" and "MST" 
> might need to retire as well. (Luckily, there is no "CST" or "PST".)
> Similar issues will come up if EU regions go to "permanent daylight 
> saving", as they have threatened to do for years.
> Whatever we do in this area, it will be a mess.
"A mess" doesn't sound good.

Apparently there is still debate of "permanent DST" v.s. "permanent 
standard time". Many arguments have been made for "permanent standard 
time" but amongst them is no discussion or recognition of the potential 
technical difficulties, disruptions, and costs associated with 
"permanent DST".  I would think the major implementers would be very 
concerned about this. I'm guessing all industries, from finance to 
transportation, would be affected and many don't realize the 
difficulties and costs they may face to adapt to the change.

As I understand it going to "permanent standard time" is simple and 
straight forward for tzdb and the entire downstream infrastructure. 
Wouldn't it be a good idea to try to inform the public and politicians 
of the technical challenges posed by "permanent DST" ?

More information about the tz mailing list