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pendulum Interval ranges and DateTime timezone conversion: working versions (tested 2026-10-16)

Build day and month ranges with pendulum Interval (Period in pendulum 2), convert the same instant between timezones, and see how DST and DateTime subtraction behave, tested fully offline.

passed6 passed · 0 failed2026-10-16 09:57 UTC
Status
passed
Last passed
2026-10-16 09:57 UTC
Tests
6 / 6
Language
Python
Runtime
Python 3.13.16
pinned versions2
pendulum@3.3.0pytest@9.1.1
run it
uv venv -q .venv && uv pip install -q --python .venv/bin/python -r requirements.txt
.venv/bin/python -m pytest -q
test environment
Python 3.13.16
linux 6.17.0-1022-azure
x64
runner: github-actions 38883899161

The code

Exactly the files that passed. Your agent can pull them with get_recipe("pendulum-period-range") (install), or see them on GitHub.

requirements.txt
pendulum==3.3.0
pytest==9.1.1
ranges.py
from __future__ import annotations

from collections.abc import Iterator

import pendulum
from pendulum import DateTime, Interval


def day_range(start: DateTime, end: DateTime) -> Iterator[DateTime]:
    return pendulum.interval(start, end).range("days")


def month_anchors(start: DateTime, end: DateTime) -> Iterator[DateTime]:
    return pendulum.interval(start, end).range("months")


def to_timezone(dt: DateTime, tz: str) -> DateTime:
    return dt.in_timezone(tz)


def span(start: DateTime, end: DateTime) -> Interval:
    return end - start
tests/test_ranges.py
import pendulum
import pytest
from ranges import day_range, month_anchors, span, to_timezone


def test_day_range_stops_before_the_end():
    start = pendulum.datetime(2024, 1, 1, 10, 30, tz="UTC")
    end = pendulum.datetime(2024, 1, 3, 9, 0, tz="UTC")
    assert [d.to_date_string() for d in day_range(start, end)] == [
        "2024-01-01",
        "2024-01-02",
    ]


def test_month_anchors_keep_the_start_day():
    start = pendulum.datetime(2024, 1, 15, tz="UTC")
    end = pendulum.datetime(2024, 4, 1, tz="UTC")
    assert [d.to_date_string() for d in month_anchors(start, end)] == [
        "2024-01-15",
        "2024-02-15",
        "2024-03-15",
    ]


def test_conversion_keeps_the_instant():
    moment = pendulum.datetime(2024, 3, 9, 12, tz="UTC")
    tokyo = to_timezone(moment, "Asia/Tokyo")
    assert tokyo == moment
    assert (tokyo.timezone_name, tokyo.hour) == ("Asia/Tokyo", 21)


def test_day_range_across_dst_keeps_local_midnight():
    start = pendulum.datetime(2024, 3, 9, tz="America/New_York")
    end = pendulum.datetime(2024, 3, 11, tz="America/New_York")
    days = list(day_range(start, end))
    assert [d.hour for d in days] == [0, 0, 0]
    assert [d.in_timezone("UTC").hour for d in days] == [5, 5, 4]


def test_subtracting_datetimes_returns_an_interval():
    start = pendulum.datetime(2024, 3, 9, tz="America/New_York")
    end = pendulum.datetime(2024, 3, 11, tz="America/New_York")
    diff = span(start, end)
    assert isinstance(diff, pendulum.Interval)
    assert diff.in_days() == 2
    assert diff.total_days() == pytest.approx(47 / 24)


def test_inverted_range_iterates_backwards():
    interval = pendulum.interval(
        pendulum.datetime(2024, 1, 5, tz="UTC"),
        pendulum.datetime(2024, 1, 1, tz="UTC"),
    )
    assert interval.invert is True
    assert [d.to_date_string() for d in interval.range("days")] == [
        "2024-01-05",
        "2024-01-04",
        "2024-01-03",
        "2024-01-02",
        "2024-01-01",
    ]
pytest.ini
[pytest]
pythonpath = .

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terminal
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