Run Semi-Annual Tasks at Midnight | CronBase

cron expression Standard
$ 0 0 1 */6 *

At midnight on the first day of January and July

This standard cron expression schedules a job to run at midnight on the first day of January and July. This semi-annual cadence is ideal for long-term maintenance tasks, such as bi-annual database archiving, compliance auditing, certificate rotations, and generating fiscal half-year financial reports without disrupting daily production workloads.

Minute
0
Hour
0
Day of Month
1
Month
*/6
Day of Week
*
How it works

Next 5 Runs

  • in 159d 3h
  • in 340d 3h
  • in 524d 3h
  • in 706d 3h
  • in 890d 3h

* Tools

Code & Implementations

Bash
#!/usr/bin/env bash
set -euo pipefail
# Script to install the semi-annual cron job safely
CRON_EXPR="0 0 1 */6 *"
JOB_CMD="/usr/local/bin/run-semi-annual-audit.sh"
LOG_FILE="/var/log/semi_annual_cron.log"
# Check if crontab is available
if ! command -v crontab &> /dev/null; then
    echo "Error: crontab utility not found." >&2
    exit 1
fi
# Backup current crontab, append new job, and reload
(crontab -l 2>/dev/null | grep -v "$JOB_CMD"; echo "$CRON_EXPR $JOB_CMD >> $LOG_FILE 2>&1") | crontab -
echo "Cron job successfully scheduled to run semi-annually."
Setup notes

Save this script as setup_cron.sh, make it executable with chmod +x, and run it as root or the user who needs to execute the task.

Last verified:

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Platform Equivalents

AWS EventBridge

Standard cron expressions often need conversion for AWS EventBridge schedules.

EventBridge Rule
cron(0 0 1 */6 ? *)

Systemd Timer

OnCalendar*-00/6-01 00:00:00

my-task.timer
[Unit]
Description=Timer for cron expression: 0 0 1 */6 *

[Timer]
OnCalendar=*-00/6-01 00:00:00
Persistent=true

[Install]
WantedBy=timers.target

Last verified:

Frequently Asked Questions

How does standard cron interpret the `/6` step in the month field?

In standard cron, the step operator `*/6` starts from the first month (January) and increments by six. This resolves to January (month 1) and July (month 7). It does not run every six months from the date of deployment; it is pinned to the calendar year.

What happens if the server timezone changes mid-year?

If the underlying system timezone changes, the next execution will align with the new timezone's midnight. To prevent unexpected shifts in financial or compliance reporting, always force your cron runtime or container environment to execute in UTC.

How can I safely test a job that only runs twice a year?

You should never wait six months to verify your job. Inject a test environment variable to bypass the schedule check, or temporarily modify the cron expression to run in the next five minutes in a staging environment to validate the execution logic and permissions.

How should I handle failures for a semi-annual job?

Since this job runs infrequently, a failure is highly critical. Implement an explicit retry policy with exponential backoff, and integrate an external alerting service (like PagerDuty or Slack webhooks) inside the execution block to immediately notify on-call engineers.

Will this job conflict with monthly or daily cron jobs?

Yes, many automated tasks run at midnight on the first of the month. To avoid CPU or database IOPS exhaustion, consider shifting this semi-annual job to a quiet hour (e.g., 3:00 AM) or running it in an isolated, auto-scaling worker pool.

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