---
id: astropy-iers-data
version: "0.2026.8.10.0.32.39"
license: BSD-3-Clause
license_treatment: permissive
maintenance: active
---

# astropy-iers-data — IERS Earth Rotation and Leap Second tables for the astropy core package

License: permissive · Maintenance: active · Downloads: 3.2M/mo

## What it is and what it does

astropy-iers-data is a data package that bundles Earth Rotation and Leap Second tables from the International Earth Rotation Service (IERS) for use by the astropy astronomy library. It contains no runtime dependencies and is designed to be pulled in automatically when astropy is installed, not to be used directly by end users. The package maintains current Python version support (3.10+) and is actively developed, with releases tracking IERS data updates.

The package exists to decouple IERS data management from astropy's core release cycle, allowing data tables to be updated independently. Users working with astropy for time-dependent astronomical calculations, coordinate transformations, or Earth orientation corrections will implicitly use this package through astropy's dependency chain, but should not install it directly.

Use it for:

- Automatic dependency installed by astropy to support Earth orientation parameter calculations in astronomical coordinate transformations.
- Providing up-to-date IERS leap second and polar motion data for time-critical astronomical observations and ephemeris calculations.
- Enabling astropy to maintain accurate Earth rotation models without requiring users to manually download or manage IERS data files.

## Worth the install?

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

Provides IERS Earth Rotation and Leap Second tables as data files for the astropy package, intended for internal use by astropy rather than direct user installation.

No—do not install this package directly. It is explicitly designed for internal use by astropy only and should be installed as an automatic dependency of astropy, not as a standalone package. If you need IERS data for astronomical calculations, install astropy instead, which will pull in this package automatically.

## Install

pip install astropy-iers-data
uv add astropy-iers-data
poetry add astropy-iers-data

## Installing astropy-iers-data

Before you install: Low install friction with no runtime dependencies. Actively maintained with a recent release; however, the package is explicitly not meant for direct user installation and should only be used as a dependency of astropy itself.

License in practice: Licensed under BSD 3-Clause (permissive), allowing free use, modification, and distribution with minimal restrictions.

Quickstart:

# This package is not meant for direct use.
# Install astropy instead:
# pip install astropy
# astropy will automatically include astropy-iers-data as a dependency.

This package should not be installed directly; it is an internal dependency of astropy and may not function correctly if used standalone.

Verify before relying:

- Whether this package can be safely installed standalone or if installation outside of astropy's dependency chain may cause issues.
- What specific IERS data tables are included and their update frequency relative to official IERS releases.

## Package facts

- License: BSD-3-Clause (permissive)
- Python support: supports_current
- Install friction: low
- Maintenance: active
- Downloads: 3.2M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

IERS earth rotation data, leap second tables astropy, astropy IERS data, earth orientation parameters, astropy internal data package, astropy-internal, iers-data, astronomy

[View on SkillFed](https://skillfed.io/packages/astropy-iers-data) · [View on PyPI](https://pypi.org/project/astropy-iers-data/)