IANA TZ Database for Backward UTC Zones

The `tzdata-backward-utc` package provides a specialized subset of the IANA Time Zone Database, specifically containing old synonyms for `Etc/UTC` and `Etc/GMT` zones, represented as a single JSON file. Maintained by Rogier Schouten, this package is part of a larger ecosystem of `tzdata` modules designed to offer granular access to time zone data. Its current stable version is `1.0.48`, updated to IANA TZ database version `2026a`, and it generally follows the release cadence of the upstream IANA TZ database, typically updating every few months to reflect the latest time zone rules, such as recent changes for Kazakhstan or Palestine. Key differentiators include its focus on a very specific historical subset of time zone data and its direct provision of the raw IANA data as a machine-readable JSON object, primarily intended for consumption by other timezone processing libraries like `timezonecomplete`, rather than being a timezone calculation library itself.