Unfortunately the IANA tzdb is less reliable than most developers would probably assume. A few years ago I was using moment-timezone for a web app and noticed

Unfortunately the IANA tzdb is less reliable than most developers would probably assume. A few years ago I was using moment-timezone for a web app and noticed it was displaying time wrong for Chinese users. Looking into the issue, I found out that the packaged tzdb version somehow thought China Standard Time was observing DST, which was a brief experiment scrapped decades ago. Digging into tzdb source, I felt like being thrown into an old style wiki page where people argue with each other back and force over the years, leaving all the historical arguments directly in comments in the source code. At times people just go with incomplete information and somewhat questionable sources, which might get corrected a decade later. You can check for yourself: https://data.iana.org/time-zones/tzdb-2021a/asia https://data.iana.org/time-zones/tzdb-2021a/asia (Btw, I can't really pinpoint the problematic version I encountered years ago now.)