CLDR zzz

Time-zone name, short.

MST

at the reference instant, Mon, Jan 2 2006, 3:04:05 PM MST

The abbreviated zone name (MST). TRAP FIELD: abbreviations are ambiguous (CST = Chicago, Cuba or China) and platform-dependent in strftime; identifiers like America/Phoenix are the reliable currency.

LanguageTokenCaveat
C / POSIX strftime%ZName or abbreviation; no bytes if no timezone information exists.
CLDR / ICU patternzShort specific non-location name (PDT); zzzz gives the long form. Falls back to a localized GMT format like GMT-8 where no abbreviation exists.
Go time layoutMST
Java DateTimeFormatterzShort DST-aware name (PST); zzzz spells it out, v ignores daylight saving.
JavaScript Intl.DateTimeFormattimeZoneName: "short"Falls back to an offset (GMT-7) where the locale has no abbreviation; "long", "shortGeneric" and "longGeneric" also exist.
PHP date()TFalls back to a GMT offset like +05 when no abbreviation is known; e gives the full identifier (Atlantic/Azores).
Python strftime%ZEmpty for naive datetimes; the name comes from the tzinfo object.
Ruby strftime%ZPlatform-dependent name, e.g. Central Daylight Time.
Rust chrono%ZTrap: when formatting, this prints the offset, not a zone abbreviation — chrono only knows offsets. Parsing skips any non-whitespace.

Definition anchored to Unicode UTS #35 — Date Field Symbol Table.