---
id: crontab
version: "1.0.5"
license: GNU LGPL v2.1
license_treatment: copyleft
maintenance: aging
---

# crontab — Parse and use crontab schedules in Python

License: copyleft · Maintenance: aging · Downloads: 1.3M/mo

## What it is and what it does

This package provides a Python interface to parse standard crontab schedule syntax and compute when a scheduled task should next run. It accepts 5–7 field crontab entries (seconds, minutes, hours, day of month, month, day of week, year) and supports common cron syntax including wildcards, ranges, step values, lists, and day/month abbreviations. It also recognizes convenience aliases like @hourly and @daily.

The main use case is determining the delay in seconds from the current time (or a specified datetime) until the next scheduled execution. The package has no runtime dependencies, making it lightweight for embedding in scheduling systems or task runners that need to calculate cron-based execution times without external service calls.

Use it for:

- Calculate next execution time for a cron job in a Python scheduler or task queue
- Validate and parse user-supplied crontab expressions in a web application
- Determine when a recurring background task should run next given a cron schedule
- Build a cron-based job runner that needs to compute delays between executions
- Convert crontab syntax to human-readable descriptions of when tasks will run

## Worth the install?

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

Parses crontab schedule expressions and calculates the delay in seconds until the next scheduled execution time.

Yes, with conditions. The package is stable, has no dependencies, and solves a specific problem well for applications that need to parse and schedule tasks using standard cron syntax. However, the aging maintenance status (no active development in over a year) and high install friction (source distribution) mean you should verify compatibility with your target Python version before relying on it for new projects. If you need active maintenance or additional scheduling features, consider alternatives.

## Install

pip install crontab
uv add crontab
poetry add crontab

## Installing crontab

Before you install: High install friction due to source distribution format. Package is in production/stable status with recent maintenance (last commit 2025-07-10) and no known vulnerabilities, but has not received active development in over a year.

License in practice: Licensed under GNU LGPL v2.1 (copyleft). Any derivative work or modification must be released under compatible terms; linking in a proprietary application requires careful license review.

Quickstart:

pip install crontab

from crontab import CronTab
from datetime import datetime

entry = CronTab('25 * * * *')
delay = entry.next(datetime(2011, 7, 17, 11, 25))
print(delay)  # 3600.0

Verify before relying:

- Whether the package works reliably with Python 3.13+ given the aging maintenance status
- Performance characteristics when parsing complex or deeply nested cron expressions

## Package facts

- License: GNU LGPL v2.1 (copyleft)
- Python support: unspecified
- Install friction: high
- Maintenance: aging
- Downloads: 1.3M/month (top 5,000 on PyPI)
- Known vulnerabilities: none known

## Tags

cron schedule parser, crontab expression calculator, next execution time, cron delay calculation, schedule timing in python, cron entry parser, job scheduling helper, scheduling, cron-parser, time-calculation

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