Cron.Extensions.Expressions

Easily create and parse cron expressions using a fluent syntax.

important

This library implements standard cron expressions - the five-field syntax, including names, macros, ranges, and lists, that predates Kubernetes by decades. It is fully compatible with Kubernetes CronJob schedules, but does not support Quartz cron expressions.

Package Details

• Kubernetes CronJob compatible. Every expression this library builds or parses is a valid Kubernetes CronJob schedule.
• Broad framework support. Targets .NET Standard 2.0 and 2.1 alongside .NET 6 through .NET 10.
• AOT and trim friendly. The assembly is annotated as AOT-compatible, so it can be used in Native AOT and trimmed deployments without tripping the trimming analyzers.
• Strong-named. The assembly is signed, which means it can be referenced from other strong-named assemblies.
• No dependencies. Nothing is added to your dependency graph.

Cron Expressions

A cron expression is a string used to define a schedule for running tasks in Unix-like systems, particularly in the context of the cron job scheduler. Cron expressions consist of five fields that define specific times or intervals for executing a command or script

The typical format of a cron expression is:

* * * * * command_to_execute
- - - - -
| | | | |
| | | | ----- Day of the week (0 - 7) (Sunday = 0 or 7)
| | | ------- Month (1 - 12)
| | --------- Day of the month (1 - 31)
| ----------- Hour (0 - 23)
------------- Minute (0 - 59)

Remembering how to construct and parse these expressions can be tricky. This package provides the CronExpression class to simplify that.

Quick Start

A few of the most common operations:

using Cron.Extensions.Expressions;

// Build one with the constructor
var midnight = new CronExpression(minute: "0", hour: "0");
midnight.ToCronExpression(); // "0 0 * * *"

// Or with the fluent helpers
var businessHours = new CronExpression()
    .EveryXMinutes(15)
    .RangeOfWeek(1, 5);
businessHours.ToCronExpression(); // "*/15 * * * 1-5"

// Parse an existing expression
var parsed = CronExpression.Parse("30 6 * * 1-5");

// Ask when it next runs
var next = parsed.GetNextExecution();

Where to Go Next

The rest of the documentation is organized by task:

Page	What it covers
Cron Expression Format	Which syntax this library accepts, and the field semantics that apply everywhere.
Building Expressions	Every way to construct a CronExpression, including the fluent helpers.
Evaluating Expressions	Computing the next run time and testing whether a given moment matches.
Validation and Errors	Every exception the library throws, what causes it, and how to fix it.
Common Recipes	Ready-to-use expressions for the schedules people need most often.
API Reference	The complete public surface.