---
id: udatetime
version: "0.0.17"
license: Apache 2.0
license_treatment: permissive
maintenance: dormant
---

# udatetime — Fast RFC3339 compliant date-time library

License: permissive · Maintenance: dormant · Downloads: 91.4K/mo

## What it is and what it does

udatetime is a C-accelerated library for parsing, formatting, and working with RFC3339-compliant date-time strings in Python. It wraps Python's standard datetime class but optimizes the hot path—string parsing and formatting—through a native C implementation. All datetime objects it creates are timezone-aware with fixed-offset timezones (no daylight savings time).

The library is designed as a drop-in replacement for code already using datetime: it exposes familiar methods like from_string, to_string, now, utcnow, fromtimestamp, and utcfromtimestamp. It supports both Python 2 and Python 3 via a C implementation, and PyPy via a pure-Python fallback. The trade-off is a high installation barrier—you must have a C compiler and Python development headers available at build time, and it only runs on POSIX systems.

Use it for:

- Parse and serialize RFC3339 timestamps in high-throughput APIs or logging systems where datetime performance matters.
- Replace datetime in time-sensitive applications that handle many timestamp conversions.
- Work with fixed-offset timezones in systems that do not need DST handling and want guaranteed UTC or regional offset behavior.
- Build services that emit or consume RFC3339 date-times, common in REST APIs and JSON payloads.

## Worth the install?

AI-flagged interpretation of the facts above — verify before relying.

udatetime provides fast RFC3339-compliant date-time parsing, formatting, and manipulation for Python, offering faster instantiation and serialization than the standard datetime library.

Yes, if you have a POSIX system with a C compiler and Python dev headers, and your code is performance-sensitive around datetime parsing or formatting. The permissive Apache 2.0 license and performance gains make it a solid choice for high-throughput services. However, the dormant maintenance status (last commit 2024-06-11) and high build friction mean you should verify it works on your target Python version before committing. Not recommended for Windows or for projects that cannot tolerate a build-time C dependency.

## Install

pip install udatetime
uv add udatetime
poetry add udatetime

## Installing udatetime

Before you install: High install friction: requires a C compiler and Python development headers (python-dev or python3-dev). The package is dormant—last commit was 2024-06-11, with no recent activity. No runtime dependencies, but the C extension build is a significant barrier on systems without a development toolchain.

License in practice: Apache 2.0 is permissive and imposes no restrictions on commercial or proprietary use. You may use, modify, and distribute udatetime freely provided you include a copy of the license and note any changes made.

Quickstart:

import udatetime

# Parse RFC3339 string to datetime
dt = udatetime.from_string("2016-07-15T12:33:20.123000+02:00")

# Serialize datetime back to RFC3339 string
result = udatetime.to_string(dt)
print(result)  # '2016-07-15T12:33:20.123000+02:00'

Requires a C compiler and Python development headers (python-dev or python3-dev on Debian/Ubuntu, python-devel or python3-devel on RHEL/CentOS). POSIX-compliant systems only; Windows support is not available.

Verify before relying:

- Whether the package works reliably on modern Python versions (3.10+) despite classifiers only listing up to 3.6.
- Current status of Windows support, given the description states only POSIX systems are supported.
- Whether the C extension builds successfully on recent Python versions without modification.

## Package facts

- License: Apache 2.0 (permissive)
- Python support: unspecified
- Install friction: high
- Maintenance: dormant
- Downloads: 91.4K/month (top 15,000 on PyPI)
- Known vulnerabilities: none known

## Tags

rfc3339 datetime parser, fast date time parsing, iso 8601 compliant datetime, timezone aware datetime, datetime serialization, high performance date handling, utc datetime library, datetime-parsing, performance-critical, rfc3339

[View on SkillFed](https://skillfed.io/packages/udatetime) · [View on PyPI](https://pypi.org/project/udatetime/)