Execute Monthly Task on the First of the Month | CronBase
0 21 1 * * Once a month on the first day at 9 PM
* In a Nutshell
The cron expression 0 21 1 * * runs Once a month on the first day at 9 PM. This cadence is critical for tasks that must align with monthly cycles, such as end-of-month financial processing, generating monthly reports, or performing archival operations. Running precisely on the first day ensures consistency and predictability for business operations that depend on this monthly schedule.
* When to use this
Use 0 21 1 * * when a recurring task needs to run Once a month on the first day at 9 PM. This schedule is commonly associated with financial processing and monthly schedules and report generation 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 0 21 1 * * 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.
# Add to crontab with: crontab -e
0 21 1 * * /usr/local/bin/run-task.sh >> /var/log/cron-tasks.log 2>&1Last verified:
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.
import cron from 'node-cron';
cron.schedule('0 21 1 * *', async () => {
console.log('[cron] running at', new Date().toISOString());
// your task logic here
}, { timezone: 'UTC' });Last verified:
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.
from apscheduler.schedulers.blocking import BlockingScheduler
from apscheduler.triggers.cron import CronTrigger
scheduler = BlockingScheduler(timezone='UTC')
@scheduler.scheduled_job(
CronTrigger.from_crontab('0 21 1 * *', timezone='UTC')
)
def run_task() -> None:
print('task running')
# your task logic here
scheduler.start()Last verified:
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.
package main
import (
"fmt"
"time"
"github.com/robfig/cron/v3"
)
func main() {
c := cron.New(cron.WithLocation(time.UTC))
_, err := c.AddFunc("0 21 1 * *", 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:
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 0 21 1 * ? is derived from 0 21 1 * * — 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 *.
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;
@Component
public class ScheduledTask {
@Scheduled(cron = "0 0 21 1 * ?")
public void runTask() {
System.out.println("task running at: " + java.time.Instant.now());
// your task logic here
}
}Last verified:
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: Allow is set because this schedule fires infrequently — parallel runs are acceptable.
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.
apiVersion: batch/v1
kind: CronJob
metadata:
name: scheduled-task
spec:
schedule: "0 21 1 * *"
concurrencyPolicy: Allow
jobTemplate:
spec:
template:
spec:
restartPolicy: OnFailure
containers:
- name: task
image: alpine:3.19
command: ["/bin/sh", "-c", "echo 'task running'"]Last verified:
AWS EventBridge Equivalent
Standard cron expressions often need conversion for AWS EventBridge schedules.
cron(0 21 1 * ? *)Frequently Asked Questions
What specific task does the `0 21 1 * *` cron expression schedule?
This expression is configured to execute a task precisely once per month, specifically on the first day of the month, at 9 PM (21:00) server time. It's ideal for recurring monthly operations.
How does this schedule handle Timezone changes and Daylight Saving Time (DST)?
Cron jobs run based on the server's configured timezone. During DST transitions, the job will execute at the scheduled time according to the server's clock, which automatically adjusts for DST, ensuring it still fires on the intended local day and hour.
How can I verify if my monthly task is running successfully?
Check your application's logs for successful execution entries or error messages related to the task. You can also monitor any output files or database entries generated by the task for completeness and accuracy.
What potential issues should I be aware of with this monthly schedule?
The primary concern is ensuring the task completes reliably on the first day of the month. If the task fails, it might not be automatically retried until the next month, potentially causing significant data gaps or operational delays.
What is a common variation or alternative for this monthly schedule?
A common variant is to schedule the task for the last day of the month instead of the first, which can be useful for different end-of-month processing needs. It's important to choose the boundary that best fits your business logic.
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