MCPInstall

cron-expression-builder

Build and validate cron expressions from natural language. Convert between human-readable schedules and cron syntax with next run preview.

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Install

Works with every agent the skills CLI supports.

npx skills add https://github.com/dkyazzentwatwa/chatgpt-skills --skill cron-expression-builder
  1. 01

    Install

    Run the command in your project. The CLI asks which agents to install for.

  2. 02

    Describe the task

    Ask your agent for something this skill covers. It loads cron-expression-builder automatically when relevant.

  3. 03

    Review the result

    The agent follows the SKILL.md steps, scripts and references bundled with the skill.

SKILL.md

The instructions your agent reads when the skill is triggered.

Cron Expression Builder

Build, parse, and validate cron expressions with natural language conversion and run time preview.

Features

  • Natural Language: Convert descriptions to cron expressions
  • Cron Parser: Parse cron to human-readable format
  • Validation: Validate cron syntax
  • Next Runs: Preview upcoming execution times
  • Presets: Common scheduling patterns
  • Both Formats: 5-field (standard) and 6-field (with seconds)

Quick Start

from cron_builder import CronBuilder

builder = CronBuilder()

# Build from natural language
cron = builder.from_text("every day at 3:30 PM")
print(cron)  # 30 15 * * *

# Parse to human-readable
description = builder.describe("0 */2 * * *")
print(description)  # "Every 2 hours"

# Get next run times
runs = builder.next_runs("30 15 * * *", count=5)
for run in runs:
    print(run)

CLI Usage

# Build from text
python cron_builder.py --from-text "every monday at 9am"

# Describe a cron expression
python cron_builder.py --describe "0 9 * * 1"

# Validate expression
python cron_builder.py --validate "0 9 * * 1"

# Get next 10 runs
python cron_builder.py --next "0 9 * * 1" --count 10

# List preset schedules
python cron_builder.py --presets

# Use preset
python cron_builder.py --preset daily_midnight

# Interactive builder
python cron_builder.py --interactive

API Reference

CronBuilder Class

class CronBuilder:
    def __init__(self, with_seconds: bool = False)

    # Building
    def from_text(self, text: str) -> str
    def build(self, minute: str = "*", hour: str = "*",
             day: str = "*", month: str = "*",
             weekday: str = "*") -> str

    # Parsing
    def describe(self, expression: str) -> str
    def parse(self, expression: str) -> dict

    # Validation
    def validate(self, expression: str) -> dict
    def is_valid(self, expression: str) -> bool

    # Execution times
    def next_runs(self, expression: str, count: int = 5,
                 from_date: datetime = None) -> list
    def matches(self, expression: str, dt: datetime) -> bool

    # Presets
    def get_preset(self, name: str) -> str
    def list_presets(self) -> dict

Cron Expression Format

5-Field Format (Standard)

┌───────────── minute (0-59)
│ ┌───────────── hour (0-23)
│ │ ┌───────────── day of month (1-31)
│ │ │ ┌───────────── month (1-12)
│ │ │ │ ┌───────────── day of week (0-6, Sun=0)
│ │ │ │ │
* * * * *

6-Field Format (With Seconds)

┌───────────── second (0-59)
│ ┌───────────── minute (0-59)
│ │ ┌───────────── hour (0-23)
│ │ │ ┌───────────── day of month (1-31)
│ │ │ │ ┌───────────── month (1-12)
│ │ │ │ │ ┌───────────── day of week (0-6)
│ │ │ │ │ │
* * * * * *

Natural Language Conversion

Supported Patterns

# Time-based
builder.from_text("every minute")        # * * * * *
builder.from_text("every 5 minutes")     # */5 * * * *
builder.from_text("every hour")          # 0 * * * *
builder.from_text("every 2 hours")       # 0 */2 * * *

# Daily
builder.from_text("every day at noon")   # 0 12 * * *
builder.from_text("daily at 3pm")        # 0 15 * * *
builder.from_text("at 3:30 PM every day")# 30 15 * * *

# Weekly
builder.from_text("every monday")        # 0 0 * * 1
builder.from_text("weekdays at 9am")     # 0 9 * * 1-5
builder.from_text("every friday at 5pm") # 0 17 * * 5

# Monthly
builder.from_text("first of every month")# 0 0 1 * *
builder.from_text("15th of each month")  # 0 0 15 * *
builder.from_text("last day of month")   # 0 0 L * *

# Special
builder.from_text("every sunday at midnight") # 0 0 * * 0
builder.from_text("twice daily")         # 0 0,12 * * *

Presets

Built-in common schedules:

PresetCronDescription
every_minute* * * * *Every minute
every_5_minutes*/5 * * * *Every 5 minutes
every_15_minutes*/15 * * * *Every 15 minutes
every_30_minutes*/30 * * * *Every 30 minutes
hourly0 * * * *Every hour
daily_midnight0 0 * * *Daily at midnight
daily_noon0 12 * * *Daily at noon
weekly_sunday0 0 * * 0Weekly on Sunday
weekly_monday0 0 * * 1Weekly on Monday
monthly0 0 1 * *First of month
quarterly0 0 1 1,4,7,10 *First day of quarter
yearly0 0 1 1 *January 1st
cron = builder.get_preset("daily_noon")
# "0 12 * * *"

Cron Description

Convert cron to human-readable:

builder.describe("30 15 * * 1-5")
# "At 3:30 PM, Monday through Friday"

builder.describe("0 */6 * * *")
# "Every 6 hours"

builder.describe("0 9 15 * *")
# "At 9:00 AM on day 15 of every month"

Validation

result = builder.validate("0 9 * * 1")

# Returns:
{
    "valid": True,
    "expression": "0 9 * * 1",
    "fields": {
        "minute": "0",
        "hour": "9",
        "day_of_month": "*",
        "month": "*",
        "day_of_week": "1"
    },
    "description": "At 9:00 AM, only on Monday"
}

# Invalid expression
result = builder.validate("60 25 * * *")
# Returns:
{
    "valid": False,
    "error": "Invalid minute: 60 (must be 0-59)"
}

Next Run Times

Preview upcoming executions:

runs = builder.next_runs("0 9 * * 1", count=5)

# Returns:
[
    "2024-01-15 09:00:00",  # Next Monday
    "2024-01-22 09:00:00",
    "2024-01-29 09:00:00",
    "2024-02-05 09:00:00",
    "2024-02-12 09:00:00"
]

Check Specific Time

from datetime import datetime

# Does this cron run at this time?
matches = builder.matches("0 9 * * 1", datetime(2024, 1, 15, 9, 0))
# True (Monday at 9 AM)

Manual Building

Build expression field by field:

# Every Monday at 9:30 AM
cron = builder.build(
    minute="30",
    hour="9",
    day="*",
    month="*",
    weekday="1"
)
# "30 9 * * 1"

# Every 15 minutes during business hours on weekdays
cron = builder.build(
    minute="*/15",
    hour="9-17",
    day="*",
    month="*",
    weekday="1-5"
)
# "*/15 9-17 * * 1-5"

Example Workflows

Schedule Builder

builder = CronBuilder()

# Create schedule from user input
schedule_text = "every weekday at 8:30 AM"
cron = builder.from_text(schedule_text)

# Validate and preview
if builder.is_valid(cron):
    print(f"Cron: {cron}")
    print(f"Description: {builder.describe(cron)}")
    print("\nNext 5 runs:")
    for run in builder.next_runs(cron, count=5):
        print(f"  {run}")

Job Scheduler Integration

# Define schedules for different jobs
jobs = {
    "backup": builder.get_preset("daily_midnight"),
    "reports": builder.from_text("every monday at 8am"),
    "cleanup": builder.from_text("first sunday of month at 2am")
}

for job_name, cron in jobs.items():
    print(f"{job_name}: {cron}")
    print(f"  Next run: {builder.next_runs(cron, count=1)[0]}")

Dependencies

  • croniter>=1.4.0 (for next run calculations)

FAQ

What does the cron-expression-builder skill do?

Build and validate cron expressions from natural language. Convert between human-readable schedules and cron syntax with next run preview.

How do I install cron-expression-builder?

Run npx skills add https://github.com/dkyazzentwatwa/chatgpt-skills --skill cron-expression-builder in your project. The skills CLI detects the agents you use and copies the skill into the right folder. For Claude Code you can also place the skill folder at ~/.claude/skills/cron-expression-builder/ (personal) or .claude/skills/cron-expression-builder/ (project).

Which AI agents can use cron-expression-builder?

Any agent that supports the open Agent Skills format (a folder with a SKILL.md file), including Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, Windsurf, Cline, OpenCode and more.

Is cron-expression-builder safe to install?

No partner security audit is available yet. Skills can run commands and scripts, so read the SKILL.md and any bundled files before installing.

Who maintains cron-expression-builder?

It is published by dkyazzentwatwa in dkyazzentwatwa/chatgpt-skills. It has 71 recorded installs.

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