TZNAMECEST

TZNAMECEST is a label used in time zone data and software libraries to denote the abbreviation used during daylight saving time for Central European Time, specifically the Central European Summer Time period. It is not a universal, officially standardized constant across all platforms, but rather a reference to the DST name that appears in a given tzdata entry or library.

Central European Time (CET) corresponds to UTC+1, while during daylight saving clocks are advanced one hour to Central European Summer Time (CEST), which is UTC+2. DST typically runs from the last Sunday in March to the last Sunday in October in many European jurisdictions, though exact dates can vary by country or policy. In the tz database, the standard time designation is CET and the daylight saving designation is CEST.

In practice, many C library implementations store time zone abbreviations in a two-element array called tzname, where tzname[0] holds the standard time abbreviation (for CET regions, CET) and tzname[1] holds the daylight saving abbreviation (CEST). The actual strings used, including whether TZNAMECEST appears in code or documentation, depend on the system’s time zone data and the locale or environment in which the program runs.

Notes on usage: TZNAMECEST is not an official, portable constant; its presence and exact form vary with tzdata updates and platform-specific implementations. It is commonly encountered in documentation or examples describing the representation of CET/CEST in software rather than as a universal standard.