udatetime
Fast RFC3339 compliant date-time library
Decision gist · record as of 2026-08-14
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.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- 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.
- High install friction: requires a C compiler and Python development headers (python-dev or python3-dev).
License · maintenance · safety
Apache 2.0 (permissive) — 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.
last release 2022-08-12 (1463 days) · last repo commit 2024-06-11 · 241 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 91,368 downloads/mo, #13,517 on PyPI
Alternatives
Verify before relying
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'- 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.
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 on this page. Verify before relying on it.
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
udatetime on PyPI
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.
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.
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'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 | Not specified |
| Install friction | High. Source build required |
| Runtime dependencies | None |
| Maintenance | Dormant 1,463 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 91,368 / month, #13,517 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableIntended Audience :: DevelopersLicense :: OSI Approved :: Apache Software LicenseNatural Language :: EnglishOperating System :: MacOSOperating System :: POSIXProgramming Language :: CProgramming Language :: PythonProgramming Language :: Python :: 2.6Programming Language :: Python :: 2.7Programming Language :: Python :: 3.4Programming Language :: Python :: 3.5Programming Language :: Python :: 3.6Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPy |
Evidence: udatetime-0.0.17-py2.7-linux-x86_64.egg; udatetime-0.0.17-py3.5-linux-x86_64.egg; udatetime-0.0.17-py3.9-linux-x86_64.egg; udatetime-0.0.17.tar.gz
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See also DateTime · strict-rfc3339 · tonyg-rfc3339 · ciso8601 · isodate · rfc3339-validator · aniso8601 · metomi-isodatetime · hightime · pycdlib