pytz

pytz brings the IANA/Olson timezone database into Python, enabling accurate cross-platform timezone calculations and daylight-saving-time-aware datetime handling. Current version is 2026.1.post1, released March 2026; versions track IANA tz database releases (typically several times per year). The pytz maintainer explicitly states that projects on Python 3.9+ should prefer the stdlib zoneinfo module (PEP 615) with the tzdata package instead — pytz is now in maintenance mode for backwards compatibility only.