Paul, I am looking at a commit you did on Jan 7,2023: https://github.com/eggert/tz/commit/600e78ba0487d82aaa97c00f08b26022d32e3470 Your commit summary reads:

* zone1970.tab (Pacific/Honolulu): Remove UM country code. This change needed because Pacific/Johston moved to ‘backward’ in 2017a, due to its not differing from Pacific/Honolulu since 1970.

For reference, "UM" is the ISO 3166 code for the *US Minor Outlying Islands* which includes Johnston Atoll. I am not clear why this is a special case for Pacific/Johnston. There are now numerous linked zones in the backward file. Generally you appear to have kept all the relevant ISO 3166 codes in zonetab1970. e.g. there are three links pointing to America/Panama; accordingly the America/Panama entry in zonetab1970 lists all the relevant codes (PA, CA, & KY). So what makes the Pacific/Johnston case differ from the others? -chris