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Use StartCalendarInterval to match the deprecation date, but do not treat it as a built-in one-shot timer. The calendar dictionary is a recurring pattern: every omitted field is a wildcard. A reliable design specifies the complete date and time, makes the action safe to repeat, records successful completion, and removes both the registered service and its plist when appropriate.
Sleep and power-off are different failure modes. Apple documents that a calendar event missed during sleep runs when the Mac wakes; a Mac that is powered off misses that occurrence and waits for the next scheduled match. The archived behavior is described in Apple’s Scheduling Timed Jobs guide, so validate the result on the macOS release you will actually use.
What launchd can—and cannot—guarantee
launchd is macOS’s service manager. A plist tells it what to launch, under which context, and which events should trigger it. For a calendar trigger, the key is StartCalendarInterval. Apple documents this as a dictionary containing fields such as Month, Day, Weekday, Hour, and Minute. Every field you omit is treated as a wildcard, so the dictionary describes a match rule rather than a durable “run exactly once” appointment.
That distinction matters near a deprecation deadline. A rule containing only day, hour, and minute can match on that day and time in every month. A rule containing month, day, hour, and minute can match again in later years because the calendar pattern has no built-in completion flag. The process, not the calendar dictionary, must decide that the intended work has already happened.
Apple’s archived explanation also separates sleep from power-off. If the Mac is asleep at the matching time, the job runs after wake. If it is shut down, that occurrence is missed; launchd waits for a later matching time. Neither statement promises that a process starts at the exact wall-clock second on every current macOS version.
Read the archived references alongside the installed system’s man pages because the programming guides are archived and launchd behavior can vary by release:
- Scheduling Timed Jobs explains calendar matching and sleep behavior.
- Creating Launch Daemons and Agents describes job locations and execution contexts.
launchd.plist(5)documents plist keys such asRunAtLoad.launchctl(1)documents service-management operations includingbootout.
Build the calendar rule around the real deprecation date
Include every field that defines the date
A narrow match should include the month, day, hour, and minute. Add Weekday only when the weekday is itself part of the requirement; otherwise it can create an accidental conjunction that never matches if the date and weekday disagree. Do not omit Month or Day merely because the event is annual or monthly unless that recurrence is intentional.
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<key>StartCalendarInterval</key>
<dict>
<key>Month</key>
<integer>11</integer>
<key>Day</key>
<integer>30</integer>
<key>Hour</key>
<integer>23</integer>
<key>Minute</key>
<integer>59</integer>
</dict>
<key>RunAtLoad</key>
<false/>This pattern has no year field in the documented set, so it may match the same month, day, and time in a future year. If the deprecation is a single historical date, your script must check a completion record or the state of the system being changed before doing anything destructive.
Keep loading separate from the calendar event
RunAtLoad defaults to false. When enabled, it launches the job as soon as the service is loaded, which can happen during installation or a reload. That is useful for a continuously available agent, but it defeats a date-only design unless the program deliberately handles the load-time invocation. Leave it false for a calendar-triggered action and test loading on a disposable copy first.
Make the action idempotent before scheduling it
Because a calendar pattern can recur and because a sleeping Mac may run a missed event after wake, the executable should be safe when invoked more than once. Idempotency means a second invocation observes that the deprecation work already completed and exits without repeating it.
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Use an explicit completion check
- Check the system state that the deprecation action is meant to change, such as a version, feature flag, or migration marker.
- Record completion only after the action succeeds. A marker written before the final operation can suppress a needed retry after a partial failure.
- Make the check and update robust against two invocations arriving close together. A lock or an atomic state transition prevents duplicate work.
- Log the decision, start time, result, and any error where the account or daemon context can write it.
This guard is what turns a recurring match rule into behavior that is effectively one-time. It also protects against a manual test launch, a reload with RunAtLoad accidentally enabled, or a future-year match.
Choose the correct launchd context
Apple distinguishes per-user agents from system daemons. A user agent normally belongs in that user’s ~/Library/LaunchAgents directory and runs in the user’s login context. A system daemon normally belongs in /Library/LaunchDaemons and runs outside a graphical login session with different privileges. The appropriate location depends on whether the deprecation action needs a user’s environment or system-wide access; it is not interchangeable.
The service domain determines how it is loaded, inspected, and removed. A process cannot reliably clean up a plist it cannot write, and a user agent should not be treated as a system daemon merely because a command works when prefixed with elevated privileges. Do not modify Apple-owned system directories, and do not use sudo as a universal repair. Grant only the permissions required by the chosen context.
Install and validate without turning the date into a surprise launch
- Write the executable first. Make it executable, keep it in the foreground, and run it manually with a dry-run or harmless test mode. Confirm that its completion check and logging work.
- Create the plist. Set a unique
Label, a validProgramArgumentsarray, the complete calendar dictionary, andRunAtLoadset to false. Use the LaunchAgent or LaunchDaemon location that matches the required context. - Validate the plist syntax. Use the plist-validation utility available on the target macOS release before loading it. A syntax error prevents registration; a syntactically valid file can still contain an incorrect date or path.
- Load it in the intended domain. Use the installed
launchctldocumentation for the target release and domain. Loading is the moment when an enabledRunAtLoadkey would fire, which is why the key should remain false for this design. - Inspect the registered service. Query the service through
launchctlin its actual user or system domain and verify the label, executable, and calendar settings. Do not infer runtime state from the plist file alone. - Test the executable independently. A manual run verifies application logic; it does not prove that launchd’s calendar match, sleep handling, permissions, or domain selection are correct.
Design cleanup as two separate operations
Self-removal has a service-management part and a filesystem part. Deleting the plist removes a file from disk; it does not, by itself, prove that launchd has unloaded the registered service. The researched launchctl reference identifies bootout as the mechanism for removing a service from its launchd domain. Use the exact syntax and authorization required by the target macOS version and domain rather than copying an unverified self-bootout command.
A safe order for completion
- Acquire the same lock used by the completion check and re-read the current state.
- Perform the deprecation action and verify its result.
- Write the completion record and a useful log entry.
- Request service removal with
launchctl bootoutin the correct domain, using the installedlaunchctl(1)manual to confirm arguments and permissions. - Remove the plist from its LaunchAgent or LaunchDaemon directory only when the process has permission and the service-removal behavior has been verified.
The exact sequence for a process booting itself out is not established by the cited material. Test it on the target release with a harmless job, confirm that the service disappears from inspection, and only then use it for an irreversible deprecation action. If self-bootout is too risky, have a separate administrator-managed cleanup step remove the service after the action records success.
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Keep the managed process in the foreground
A launchd-managed process must not daemonize itself. Forking and backgrounding can make launchd believe the managed process exited while the real work continues in an unmanaged child. Keep the main process attached to launchd, handle termination cleanly, and arrange for SIGTERM to stop work or finish a safe checkpoint. This avoids orphaned work during a reload, shutdown, or service removal.
Do not confuse “the script returned” with “the deprecation completed.” Return a failure status when the action did not finish, preserve enough log detail to diagnose it, and let the idempotent retry logic decide whether a later calendar match can safely try again.
Sleep versus power-off: plan for both
| Mac state at the scheduled time | Documented result | Design implication |
|---|---|---|
| Asleep | Apple says the calendar job runs when the computer wakes. | Make the action safe to run later than the nominal time and check whether the deprecation is still valid. |
| Powered off | The scheduled occurrence is missed and launchd waits for the next designated match. | Provide a recovery path, such as a manual run or a later matching window, if missing the date is unacceptable. |
These behaviors come from Apple’s archived Scheduling Timed Jobs documentation. They do not establish exact behavior for every current macOS release, network time adjustment, time zone, or daylight-saving transition.
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Four pitfalls to watch for
1. Wildcard recurrence
Omitting a calendar field broadens the match. A day/hour/minute rule can fire in every month, and a month/day/time rule can recur in later years. Read the dictionary as a pattern and list every field that defines the intended date.
2. Assuming “once” is built in
StartCalendarInterval does not supply a completion state. Use an idempotent program, an explicit success record, and cleanup that is independent of the calendar match.
3. Deleting the plist but leaving the service loaded
Filesystem deletion and service removal are different operations. Verify the registered service in its domain, use the documented bootout mechanism, and then confirm that the plist is gone if self-deletion is part of the design.
4. Ignoring load timing or process lifetime
Enabling RunAtLoad can execute the action during installation or reload. Daemonizing can detach work from launchd. Keep RunAtLoad false for a date-only trigger and keep the managed process in the foreground.
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Debugging checks that reveal the real failure
- It runs immediately: inspect
RunAtLoad, loading history, and whether a manual test invoked the executable. A calendar dictionary does not suppress an enabled load-time launch. - It runs on unexpected dates: compare every calendar field with the intended date; an omitted field is a wildcard.
- It never runs: check the executable path, permissions, plist syntax, service domain, and whether the Mac was powered off at the only matching time.
- The file is gone but the job appears registered: inspect the domain with
launchctl; remove the service with the target release’s documentedbootoutsyntax. - The plist says it is disabled: do not treat the
Disabledkey as proof that a job is or is not loaded. Inspect the registered service instead, as cautioned inlaunchd.plist(5).
Validate wall-clock assumptions before relying on the deadline
The cited material does not establish current-version time-zone or daylight-saving behavior for this exact use case. State the macOS release, configured time zone, and intended local wall-clock time in your deployment notes. If the deprecation event depends on a boundary such as midnight or a daylight-saving transition, test that case on the target release or add an application-level time check that refuses to act outside the intended window.
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Pre-deployment checklist
- The plist contains all date fields needed to avoid accidental recurrence.
RunAtLoadis false unless an intentional load-time invocation is handled.- The executable is idempotent, logs outcomes, and records completion only after success.
- The LaunchAgent or LaunchDaemon location matches the required privilege and domain.
- The process remains in the foreground and handles
SIGTERM. - Sleep and power-off recovery behavior is documented for the operator.
- Service removal with
bootoutand plist deletion have been tested separately on the target macOS release. - Time-zone and daylight-saving assumptions have been validated where the deadline is local-time sensitive.
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