Looks like the negative DST has already caused problems in the past and applications that can't handle it (ICU & OpenJDK) have to build tzdata as per the rearguard section / ziguard.awk.
I have to say these time zone files are fascinating. Any place/time when a jurisdiction has changed the definition of time is in those files, along with a detailed history of why.
Example, California had an energy crisis soon after WWII, and changed when day light savings started/ended. There are time zone rules that track this history exactly, including a note about how clocks lost 6 minutes a day because PG&E changed AC from 60 to 59.5 Hz:
Example, California had an energy crisis soon after WWII, and changed when day light savings started/ended. There are time zone rules that track this history exactly, including a note about how clocks lost 6 minutes a day because PG&E changed AC from 60 to 59.5 Hz:
https://github.com/eggert/tz/blob/71faa2a55db2c9f21f4099b58c...