pytz is a Python library that brings the IANA/Olson timezone database into the Python runtime, enabling accurate, cross-platform timezone calculations for all the world’s timezones. It addresses a major limitation of Python’s built-in datetime.tzinfo by providing consistent support for daylight-saving transitions, historical offset changes, and ambiguous times (such as the end of DST). With pytz, developers can convert naïve datetime objects into timezone-aware ones, shift between timezones, and safely perform arithmetic across DST boundaries with methods like localize() and normalize(). Although Python 3.9 and newer include better built-in timezone support (via zoneinfo and external packages like tzdata), pytz remains widely used—especially in legacy codebases or in environments where backward compatibility matters.
Features
- Full implementation of the IANA/Olson timezone database in Python
- Methods to localize naïve datetimes and to normalize timezone transitions (especially around DST)
- Lists of supported timezones (all_timezones, common_timezones) and country-to-timezones mappings
- Works across a broad range of Python versions, including legacy 2.x and early 3.x versions
- MIT-licensed, well-tested and mature library designed for production use
- Clear API for timezone conversion, offset handling, and safe arithmetic in timezone-aware contexts
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