Understand QCBM Exact Backup Times, Joomla Time Zones, and Task Polling

QCBM separates a Profile's intended backup time from Joomla's task polling interval. The Profile says when a backup becomes due in the Joomla site timezone; the Joomla Scheduled Task periodically checks for due work and starts it on the first successful check at or after that time.

This distinction explains why a backup configured for an exact local time may start a few minutes later without the schedule being wrong.

Profile Times Use the Joomla Site Timezone

When you edit a QCBM Profile, the Schedule section identifies the Joomla site timezone. Daily, weekly, and monthly run times are interpreted in that timezone. Hourly schedules use the selected minute within each local hour.

QCBM converts scheduled occurrences as needed for storage and comparison, but the administrator-facing schedule is based on the Joomla site's configured timezone rather than the browser's local timezone.

The Default Polling Interval Is 15 Minutes

The canonical QC Backup Manager Scheduled Backups Joomla task is installed with a 15-minute interval. Each execution asks QCBM whether a published Profile has reached an exact scheduled occurrence.

That means the task does not need to execute at every Profile's exact minute. It only needs to run often enough to notice due occurrences promptly.

Example: A Daily Backup at 02:00

Suppose a Profile is configured for 02:00 in the Joomla site timezone. If Joomla runs the QCBM scheduled-backup task at 01:55 and 02:10, the Profile is not due at 01:55. At 02:10, QCBM sees that the 02:00 occurrence is due and can start it.

The 10-minute difference is polling delay, not a change to the saved Profile time. QCBM's Backups scheduler card explicitly describes scheduled work as starting on the first task check at or after the selected time.

Weekly and Monthly Scheduling

Weekly Profiles combine the selected local time with one or more selected weekdays. A weekly schedule must contain at least one weekday.

Monthly Profiles combine a selected local time with a day of the month. When the requested day does not exist in a shorter month, QCBM uses that month's final day rather than skipping the month entirely.

What “Every Scheduler Check” Means

An Every scheduler check Profile is evaluated whenever the scheduled-backup task runs, but QCBM still applies a minimum cooldown. It does not intentionally create a new Backup Set on every individual scheduler trigger while a recent occurrence or active job is already present.

Use this option only when very frequent backup eligibility is actually appropriate for the site.

Retry Timing Is Separate from Calendar Timing

The Profile's Retry wait after a failed attempt applies to the same scheduled occurrence after a failed, running, or pending attempt. Current choices range from 15 minutes through 24 hours.

A retry wait does not rewrite tomorrow's daily time, next week's weekday, or next month's day. It controls how quickly QCBM may try the same due occurrence again.

Persistent Jobs Prevent Polling from Creating Duplicates

Scheduled backups use the same persistent, resumable job architecture as manual backups. If the scheduler runs again while a scheduled Backup Set is still active, QCBM advances the existing job rather than starting a duplicate after another task poll.

If a manual persistent backup is already active, scheduled creation can be deferred until the conflicting backup-create operation is available.

Daylight Saving Time and Timezone Changes

Because Profile times are interpreted through Joomla's site timezone, daylight-saving transitions and deliberate timezone changes affect the local-time schedule. If you change the Joomla timezone, review important Profile schedules afterward and confirm the displayed Next time matches your intent.

Where to Verify the Timing

Open Components > QC Backup Manager > Backups and review Published profile schedules. QCBM displays the saved schedule description, the next due time, and the last successful scheduled backup for each published scheduled Profile.

If a due time passes without a run, compare that Profile information with the Joomla task's last/next execution. A correct Profile cannot run automatically if Joomla is not polling scheduled tasks.

Community Discussion

Want to compare workflows, share practical tips, or discuss how you use this QCBM feature? Visit the QC Backup Manager Community. For private support, bug reports, account-specific issues, or feature requests, use the QuantaCade support system.