tznn

Tiny helper for IANA time zones and abbreviations.

This package provides a small utility class backed by a static mapping in timezone.json to:

• List available IANA time zone names
• Look up the time zone abbreviation (e.g., SGT, EDT) for a given zone

Notes:

• Abbreviations are static values from timezone.json and are not date-aware (no DST transitions).
• On Windows, tzdata is listed as a dependency in case you choose to extend functionality using IANA tzdata; the current implementation only reads timezone.json and does not require system tzdata at runtime.

Install

From the project root:

pip install .

For development (tests, etc.):

pip install -r requirements.txt

Quick start

from tznn import tznn

tz = tznn()

# 1) Get a sorted list of available IANA time zone names
zones = tz.get_available_time_zones()
print(len(zones), zones[:5])

# 2) Get the abbreviation for a known time zone
print(tz.get_abbr("Asia/Singapore"))      # -> "SGT"
print(tz.get_abbr("America/New_York"))    # -> e.g., "EDT" per timezone.json

# 3) Get the full mapping of zone -> abbreviation
mapping = tz.get_all_available_time_zones()
print(mapping["America/New_York"])        # -> "EDT"

Why use this package?

Default Python libraries do not provide a simple way to get static time zone abbreviations from IANA zone names. This package fills that gap with a lightweight solution. Example :

from datetime import datetime
from zoneinfo import ZoneInfo

dt_utc = datetime(2025, 9, 23, 3, 2, 7)
dt_vn = dt_utc.astimezone(ZoneInfo("Asia/Ho_Chi_Minh"))
print(dt_vn.strftime("%d/%m/%Y %H:%M:%S %Z %z"))  # → 23/09/2025 10:02:07 ICT +0700

The result is 23/09/2025 02:02:07 +07 +0700 but expectation should be 23/09/2025 10:02:07 ICT +0700

API

Class: tznn

• get_available_time_zones() -> list[str]

  • Returns a sorted list of all IANA zone names present in timezone.json.

• get_all_available_time_zones() -> dict[str, str]

  • Returns the entire mapping of zone_name -> abbreviation loaded from timezone.json.

• get_abbr(tz_name: str) -> str

  • Returns the abbreviation for the given IANA time zone name.
  • Raises ValueError if the zone name is not found in the mapping.

Data source and limitations

• Data is loaded from the local timezone.json file included in the repository.
• Abbreviations are static and may not reflect historical or future DST changes. If you need date-aware abbreviations, consider using Python's zoneinfo module (Python 3.9+) together with an appropriate tz database.

Testing

Run the test suite from the project root:

pytest -q

The tests validate:

• The list of available zones is sorted and non-empty.
• The mapping includes known zones and string abbreviations.
• get_abbr returns correct abbreviations and raises on invalid zones.

Roadmap (ideas)

• Optional date-aware abbreviation lookup using zoneinfo (or pytz for older Pythons).
• Utilities for DST-aware conversions and current time by zone.

Knowledge

• https://adamj.eu/tech/2021/05/06/how-to-list-all-timezones-in-python/
• https://stackoverflow.com/questions/78580391/zoneinfo-is-missing-timezone-names-that-pytz-has
• https://docs.python.org/3/library/zoneinfo.html
• https://github.com/python/tzdata/issues/111
• https://discuss.python.org/t/get-local-time-zone/4169/10