TimeZone.dstName

string dstName() @property @safe const scope nothrow

Typically, the abbreviation (generally 3 or 4 letters) for the time zone when DST is in effect (e.g. PDT). It is not necessarily unique.

However, on Windows, it may be the unabbreviated name (e.g. Pacific Daylight Time). Regardless, it is not the same as name.