[tz] Weird PST8PDT and EST5EDT behavior on Alpine Linux

[Paul Eggert]

On 2024-03-06 07:39, James Cloos via tz wrote:

> (I must say it was a bit anoying that the library kept the original
> definition of EST5EDT et alia rathar than moving with the legislation.
> But only a bit.)

So Openwrt uses pre-2007 US daylight saving rules for TZ='EST5EDT'? 
That's puzzling. I thought Openwrt is based on musl, which ignores DST 
for that TZ setting (a behavior that POSIX allows). I'm a bit curious as 
to what's going on there.


> So I have to use EST5EDT,M3.2.0/2:00:00,M11.1.0/2:00:00
> for the timezone.  (The explicit /2:00:00 might be avoidable, but the
> use of self documenting data can be beneficial.)

For a fully self-documented TZ setting you could use this:

<EST>+05:00:00<EDT>+04:00:00,M3.2.0/+02:00:00,M11.1.0/+02:00:00

However, this sort of thing tends to be error-prone; e.g., suppose I 
forgot a colon?

'zic' attempts to generate the shortest equivalent TZ setting. On my 
machine /usr/share/zoneinfo/America/New_York ends with this equivalent:

EST5EDT,M3.2.0,M11.1.0

which I find more readable. I'm used to TZ strings, though, so that 
colors my opinion.