Run Checks Every 20 Minutes

cron expression Standard

$ */20 * * * *

→

Every twenty minutes, all day

*/20

Minute

Hour

Day of Month

Month

Day of Week

* In a Nutshell

The cron expression */20 * * * * runs Every twenty minutes, all day. Sub-hourly schedules are critical for near real-time operations like API polling or data synchronization. Without them, data staleness can lead to outdated information, impacting user experience and operational efficiency.

* When to use this

Use */20 * * * * when a recurring task needs to run Every twenty minutes, all day. This schedule is commonly associated with api polling and minute intervals workloads. It uses Standard (5-Field POSIX) syntax, supported by Unix cron daemons, cloud schedulers such as AWS EventBridge, and container orchestration platforms such as Kubernetes CronJob.

CronBase parses */20 * * * * using a dialect-aware rules engine that identifies the Standard (5-Field POSIX) format, validates field structure against the Standard (5-Field POSIX) specification, and produces the translation above. Next run times are calculated by forward-scanning from the current UTC clock. Learn how CronBase works.

Platform Implementations

Bash

Prerequisites

Unix/Linux host with a cron daemon running (vixie-cron, cronie, or systemd-cron). The script at /usr/local/bin/run-task.sh must exist and be executable (chmod +x).

Configuration

Run crontab -e to open the crontab editor. Cron reads the server's local timezone; prefix with CRON_TZ=UTC before the expression to pin to UTC. Always redirect output with >> /var/log/cron-tasks.log 2>&1 to capture both stdout and stderr.

Gotchas

Cron jobs inherit a minimal PATH — use full binary paths or set PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin at the top of the crontab. For sub-hourly schedules, add flock -n /tmp/run-task.lock before the command to skip overlapping runs if the previous execution is still running.

bash

# Add to crontab with: crontab -e
*/20 * * * * /usr/local/bin/run-task.sh >> /var/log/cron-tasks.log 2>&1

Last verified: April 11, 2026

Nodejs

Prerequisites

Node.js 18+ with node-cron installed (npm install node-cron). Add "type": "module" to package.json to use the import syntax shown above.

Configuration

Pass { timezone: 'UTC' } as the third argument to cron.schedule(). Without this option the schedule uses the Node.js process timezone, which shifts during DST transitions when servers are not pinned to UTC.

Gotchas

node-cron uses standard 5-field cron syntax — not Quartz 6-field. If your job runs longer than the schedule interval the next trigger fires while the previous is still executing. Use a boolean guard or a queue to skip concurrent runs rather than relying on the scheduler to enforce it.

nodejs

import cron from 'node-cron';

cron.schedule('*/20 * * * *', async () => {
  console.log('[cron] running at', new Date().toISOString());
  // your task logic here
}, { timezone: 'UTC' });

Last verified: April 11, 2026

Python

Prerequisites

Python 3.8+ with apscheduler installed (pip install apscheduler). For Python 3.12+ use apscheduler>=3.10.

Configuration

CronTrigger.from_crontab() accepts a standard 5-field cron string. Always pass timezone='UTC' to both the BlockingScheduler constructor and the trigger to ensure consistent scheduling regardless of the server's locale.

Gotchas

BlockingScheduler.start() blocks the calling thread indefinitely. For a web application, use BackgroundScheduler instead and call scheduler.start() at application startup. APScheduler logs missed fires if the process is stopped and restarted — configure misfire_grace_time (in seconds) to control how late a missed job is allowed to run.

python

from apscheduler.schedulers.blocking import BlockingScheduler
from apscheduler.triggers.cron import CronTrigger

scheduler = BlockingScheduler(timezone='UTC')

@scheduler.scheduled_job(
    CronTrigger.from_crontab('*/20 * * * *', timezone='UTC')
)
def run_task() -> None:
    print('task running')
    # your task logic here

scheduler.start()

Last verified: April 11, 2026

Golang

Prerequisites

Go 1.18+ and github.com/robfig/cron/v3 (go get github.com/robfig/cron/v3).

Configuration

Always create the scheduler with cron.New(cron.WithLocation(time.UTC)). Without WithLocation, the library defaults to the server's local timezone. Call c.Start() to begin the scheduler, then block with select {} to keep the process alive.

Gotchas

robfig/cron v3 uses standard 5-field cron expressions by default. To add second-level precision (6 fields), pass cron.WithSeconds() to cron.New() — but this changes field positions, so never mix syntaxes in the same scheduler. Always check the error returned by c.AddFunc() — a malformed expression is silently ignored without it.

golang

package main

import (
	"fmt"
	"time"

	"github.com/robfig/cron/v3"
)

func main() {
	c := cron.New(cron.WithLocation(time.UTC))
	_, err := c.AddFunc("*/20 * * * *", func() {
		fmt.Println("task running at", time.Now().UTC())
		// your task logic here
	})
	if err != nil {
		panic(err)
	}
	c.Start()
	defer c.Stop()
	select {}
}

Last verified: April 11, 2026

Java

Prerequisites

Spring Boot 2.7+ (or Spring Framework 5.3+) with spring-context on the classpath. Annotate your @SpringBootApplication class with @EnableScheduling — without it, @Scheduled methods are silently ignored.

Configuration

Spring @Scheduled uses a 6-field Quartz-style expression: [sec] [min] [hr] [dom] [mon] [dow]. The expression 0 */20 * * * ? is derived from */20 * * * * — a leading 0 is prepended for the seconds field, and ? replaces the unconstrained day field.

Gotchas

Standard Unix cron has 5 fields; Spring requires 6. Pasting a 5-field expression directly into @Scheduled shifts every field by one and the job misfires silently. Use ? for either dom or dow — Quartz does not allow both to be *.

java

import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

@Component
public class ScheduledTask {

    @Scheduled(cron = "0 */20 * * * ?")
    public void runTask() {
        System.out.println("task running at: " + java.time.Instant.now());
        // your task logic here
    }
}

Last verified: April 11, 2026

Kubernetes

Prerequisites

Kubernetes 1.21+ (CronJob API is GA). kubectl configured with cluster access. Container image must be pullable from within the cluster.

Configuration

Apply with kubectl apply -f cronjob.yaml. Check status with kubectl get cronjobs and inspect run history with kubectl get jobs. concurrencyPolicy: Forbid is set because this schedule fires sub-hourly — overlapping runs would cause contention.

Gotchas

Without startingDeadlineSeconds, a missed job (e.g., due to cluster downtime) triggers as soon as the controller recovers. Kubernetes 1.25+ supports timeZone: UTC in the spec to avoid timezone ambiguity. Keep successfulJobsHistoryLimit and failedJobsHistoryLimit low to avoid accumulating stale Job objects in the cluster.

kubernetes

apiVersion: batch/v1
kind: CronJob
metadata:
  name: scheduled-task
spec:
  schedule: "*/20 * * * *"
  concurrencyPolicy: Forbid
  jobTemplate:
    spec:
      template:
        spec:
          restartPolicy: OnFailure
          containers:
          - name: task
            image: alpine:3.19
            command: ["/bin/sh", "-c", "echo 'task running'"]

Last verified: April 11, 2026

AWS EventBridge Equivalent

Standard cron expressions often need conversion for AWS EventBridge schedules.

EventBridge Rule

cron(*/20 * * * ? *)

Frequently Asked Questions

What does the */20 * * * * cron expression do?

The `*/20 * * * *` cron expression triggers a task to run at intervals of 20 minutes, every hour, every day. This means it will execute at 00, 20, and 40 minutes past every hour.

How does this schedule handle time zones and daylight saving time?

Cron schedules typically run based on the server's local time. Be mindful of potential shifts during daylight saving time changes, as this might temporarily alter the precise clock time when your job executes.

How can I verify that my job is running every 20 minutes?

Monitor your job logs for execution timestamps. You should observe entries appearing consistently every 20 minutes throughout the day, confirming the schedule is active and the job is triggering correctly.

What are potential issues with running jobs every 20 minutes?

A key concern is overlapping runs if a job takes longer than 20 minutes to complete. This can overload resources or cause unexpected behavior, so ensure your task duration is always less than the interval.

What is a common variation of this schedule?

A common variant is to run every 10 minutes instead, which involves widening the interval slightly for less frequent checks than every 5 minutes, but more often than hourly.