isoduration
Operations with ISO 8601 durations
Decision gist · record as of 2026-08-14
Yes, but with caution. The library solves a real gap—timedelta cannot represent years or months—and has low install friction. However, it is abandoned and will not receive updates. Install it only if you need ISO 8601 duration parsing with year/month support and are comfortable maintaining a frozen dependency. For new projects, verify whether an actively maintained alternative exists or whether you can work around the limitation with timedelta.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Requires Python 3.7 or later.
- Low install friction with a single runtime dependency (arrow).
- However, the package is abandoned—last release was 2020-11-01 and no commits since 2021-11-26.
License · maintenance · safety
permissive license (permissive) — Licensed under ISC (permissive), so you can use it freely in commercial and private projects without restriction, but the abandoned status means you assume all maintenance risk.
last release 2020-11-01 (2112 days) · last repo commit 2021-11-26 · 31 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 50,649,753 downloads/mo, #574 on PyPI
Alternatives
Verify before relying
pip install isoduration
from isoduration import parse_duration, format_duration
from datetime import datetime
duration = parse_duration("P3Y6M4DT12H30M5S")
result = datetime(2020, 3, 15) + duration
formatted = format_duration(duration)- Whether arrow dependency is actively maintained and whether its updates could affect isoduration compatibility.
- Real-world performance and correctness on edge cases not covered in the description excerpt.
What it is and what it does
isoduration is a Python library for parsing, manipulating, and formatting ISO 8601 duration strings. Unlike the standard library's timedelta, which cannot represent durations with years or months, isoduration provides a Duration type that splits durations into date and time components (years, months, days, hours, minutes, seconds), each stored as a Decimal for precision. You can parse ISO strings into Duration objects, perform arithmetic by adding or subtracting them from Python datetimes, compare durations, negate them, and format them back to ISO notation.
The package depends on arrow for datetime handling and is designed to address limitations in the older isodate library by using proper parsing instead of regular expressions and providing a more uniform API. However, the package has been abandoned since late 2021 with no further development, meaning it will not receive updates for new Python versions, security issues, or bug fixes.
Use it for
- Parse ISO 8601 duration strings from APIs or configuration files and apply them to datetime calculations.
- Calculate future or past dates by adding/subtracting durations that include years or months (impossible with timedelta).
- Store durations as dictionary keys or set members using the hashable Duration type.
- Format Duration objects back to ISO 8601 strings for API responses or data export.
- Handle scheduling or recurrence logic that requires year/month granularity beyond what timedelta supports.
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes, but with caution.
The library solves a real gap—timedelta cannot represent years or months—and has low install friction. However, it is abandoned and will not receive updates. Install it only if you need ISO 8601 duration parsing with year/month support and are comfortable maintaining a frozen dependency. For new projects, verify whether an actively maintained alternative exists or whether you can work around the limitation with timedelta.
Install
isoduration on PyPI
Before you install
Low install friction with a single runtime dependency (arrow). However, the package is abandoned—last release was 2020-11-01 and no commits since 2021-11-26. It will not receive bug fixes or security updates, though no vulnerabilities are currently known.
Requires Python 3.7 or later.
License in practice
Licensed under ISC (permissive), so you can use it freely in commercial and private projects without restriction, but the abandoned status means you assume all maintenance risk.
Quickstart
pip install isoduration
from isoduration import parse_duration, format_duration
from datetime import datetime
duration = parse_duration("P3Y6M4DT12H30M5S")
result = datetime(2020, 3, 15) + duration
formatted = format_duration(duration)Verify before relying
- Whether arrow dependency is actively maintained and whether its updates could affect isoduration compatibility.
- Real-world performance and correctness on edge cases not covered in the description excerpt.
Package facts
| License | permissive license permissive |
| Python support | Supports the current Python release >=3.7 |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 1 packagearrow |
| Maintenance | Abandoned 2,112 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 50,649,753 / month, #574 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 4 - BetaIntended Audience :: DevelopersLicense :: OSI Approved :: ISC License (ISCL)Operating System :: OS IndependentProgramming Language :: Python :: 3Topic :: Software Development :: Libraries :: Python Modules |
Evidence: isoduration-20.11.0-py3-none-any.whl
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See also isodate · metomi-isodatetime · delta · aniso8601 · iso8601 · ciso8601 · isoweek · backports-datetime-fromisoformat · pytimeparse2 · parse