tzdata

tzdata is a data-only Python package containing zic-compiled binaries for the IANA time zone database, maintained by the CPython core developers. It serves as a cross-platform fallback for the standard library's zoneinfo module (Python 3.9+, PEP 615) on systems that lack system-level zone data — most critically Windows. The current version is 2025.3 (wrapping upstream IANA tzdata 2025c). Releases track IANA upstream closely, typically producing between 3 and 10+ releases per year in response to real-world timezone rule changes.