cron

A Go Cron parser library based on github.com/robfig/cron/v3. It provides more intuitive, semantic custom descriptor support on top of standard Cron expressions, such as @every, @daily, @weekly, and @monthly.

Features

• Semantic Descriptors: Supports custom syntax that is easier to read than standard Cron.
• Flexible Time Settings: Supports specifying specific time points (24-hour format) in @daily, @weekly, and @monthly.
• Multiple Time Points: Allows using comma , to separate multiple time points.
• Last N Days of Month Support: Unique L and L-n syntax for targeting the last day or the Nth day from the end of the month.
• Backward Compatibility: Fully compatible with robfig/cron/v3 standard Cron expressions.

Installation

go get github.com/hjhsamuel/cron

Quick Start

package main

import (
	"fmt"
	"time"
	"github.com/hjhsamuel/cron"
)

func main() {
	// Parse custom expression
	sch, err := cron.Parse("@monthly L 23:00") // 23:00 on the last day of every month
	if err != nil {
		panic(err)
	}

	next := sch.Next(time.Now())
	fmt.Printf("Next execution time: %v\n", next)
	
	// Default using the seconds field
	cron.New()
}

Supported Formats

@every

Executes at the specified time interval.

• @every 10s: executes every 10 seconds
• @every 1h30m: executes every 1 hour and 30 minutes

@daily

Executes at the specified time(s) every day. Supports comma-separated multiple times.

• @daily 5:00: executes at 5:00 every day
• @daily 0:00,12:00: executes at 0:00 and 12:00 every day

@weekly

Executes at the specified day(s) and time(s) every week.

• @weekly 1 5:00: executes at 5:00 every Monday
• @weekly 1-5 9:00: executes at 9:00 from Monday to Friday
• @weekly 0,6 10:00: executes at 10:00 on Sunday and Saturday (both 0 and 7 represent Sunday)

@monthly

Executes at the specified date(s) and time(s) every month. Supports special L syntax.

• @monthly 1 5:00: executes at 5:00 on the 1st of every month
• @monthly 1,15,L 0:00: executes at 0:00 on the 1st, 15th, and the last day of every month
• @monthly L-1 23:59: executes at 23:59 on the second to last day of every month

Special Symbol Description

Symbol	Description	Example
,	Conjunction (AND)	0:00,12:00 (executes at both time points)
-	Range (BETWEEN)	1-5 (from day 1 to day 5)
L	Last day of the month	@monthly L 5:00
L-n	The (n+1)th day from the end of the month	L-1 means the second to last day, L-2 means the third to last day

Notice: For the L-n syntax, if the total number of days in the current month is less than n, it will fallback to executing on the first day (1st) of that month.

License

Apache 2.0