%z for TZNAME with 2024b

[meain]

In 2024b quite a few values for FORMAT seems to have been replaced with %z and this ends up in the TZNAME value generated. For example, here is 2024a and 2024b.

# From Paul Eggert (2002-10-22)
# <http://webexhibits.org/daylightsaving/g.html> says Rothera is -03 all ye
ar.
#
# Zone  NAME            STDOFF  RULES   FORMAT  [UNTIL]
Zone Antarctica/Rothera 0       -       -00     1976 Dec  1
                        -3:00   -       -03

# From Paul Eggert (2002-10-22)
# <http://webexhibits.org/daylightsaving/g.html> says Rothera is -03 all ye
ar.
#
# Zone  NAME            STDOFF  RULES   FORMAT  [UNTIL]
Zone Antarctica/Rothera 0       -       -00     1976 Dec  1
                        -3:00   -       %z

I'm assuming this is not the expected behavior? My knowledge of how timezones work is relatively limited so feel free to let me know if I have an incorrect understanding about this.

[winterz]

yes, this is a change in tzdata2024b. from the NEWS file:

The main data form now uses %z.

however, I'm with you in that I have no idea what this means for vzic and consumers of the generated zoneinfo files.

I'm so unsure about it that I've decided to keep 2024a zoneinfo for the upcoming libical 3.0.19 release

unless someone can enlighten us.