timeZoneName property
String timeZoneNameThe time zone name.
This value is provided by the operating system and may be an abbreviation or a full name.
In the browser or on Unix-like systems commonly returns abbreviations, such as "CET" or "CEST". On Windows returns the full name, for example "Pacific Standard Time".
Source
external String get timeZoneName;
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Licensed under the Creative Commons Attribution-ShareAlike License v4.0.
https://api.dartlang.org/stable/1.24.3/dart-core/DateTime/timeZoneName.html