218542 2020-11-03 16:14:21 -0800 Incorrect timezone returned for Buenos Aires 2021-02-01 02:20:28 -0800 1 1 1 Unclassified WebKit JavaScriptCore Safari 14 All All NEW InRadar P2 Normal --- 218829 1 mwade webkit-unassigned ap mmaxfield smoley webkit-bug-importer ysuzuki oldest_to_newest 1704266 0 mwade 2020-11-03 16:14:21 -0800 1. Set OS timezone to Buenos Aires 2. Open Javascript console and run: Intl.DateTimeFormat().resolvedOptions().timeZone Expected result: "America/Argentina/Buenos_Aires" Actual result: "America/Buenos_Aires" See https://www.iana.org/time-zones for latest timezones. America/Buenos_Aires is obsolete and not in the latest version, America/Argentina/Buenos_Aires is correct. Issue possibly applies to other timezones in Argentina. Repeating the same steps above in Firefox gives the expected result: "America/Argentina/Buenos_Aires". 1704283 1 ap 2020-11-03 16:49:25 -0800 Presumably this will fix itself once macOS and iOS have an updated version of ICU? 1704324 2 ysuzuki 2020-11-03 20:40:49 -0800 Unfortunately, as of now, I think the latest ICU does not handle it correctly. This is a bug of ICU's TimeZone canonicalization. V8 shows the same behavior, because V8 is doing similar thing to JSC, and both shows the wrong result because ICU does not canonicalize it correctly. 1704491 3 webkit-bug-importer 2020-11-04 10:42:20 -0800 <rdar://problem/71042560>