Tracking down a calendar that will not update

An event added on the iPhone this morning is not on the Mac this afternoon. Or the Mac has it and the phone does not. Or both devices have it, but one shows it an hour off. These look like the same problem and they are not, because a Mac and an iPhone do not sync calendars to each other. Each device syncs separately to an account, and the event only appears in both places because both devices are talking to the same account.

That distinction decides everything that follows. A missing event is not evidence that syncing is broken in general. It is evidence that one device is not talking to the account that holds that particular event. The fastest route to a fix is to find out which account that is before touching a single setting.

Establish which account owns the event

Open Calendar on the Mac and show the calendar list with View then Show Calendar List. The list is grouped by account: iCloud, Google, Exchange, On My Mac, and any subscribed calendars, each under its own heading. Find the calendar the event was written into and note the heading above it.

Four possibilities, and each has a different failure mode.

If the calendar sits under On My Mac, the event exists only on that Mac. There is no account behind it and nothing to sync. Calendars in that section are local files, and an event placed there will never reach a phone no matter what is toggled. This catches more people than any other cause, because Calendar quietly uses a local calendar when no account is set as the default.

If it sits under iCloud, the event is in iCloud and both devices need iCloud Calendars switched on. If it sits under a Google account, the event is in Google Calendar and the rules about which calendars sync are Google's, not Apple's. If it sits under Exchange, the server controls the refresh behaviour and some features are limited by policy.

On the iPhone, the same check is in the Calendars tab at the bottom of the Calendar app. The list is grouped the same way. If the account heading you saw on the Mac is absent from the phone entirely, the account is not configured there, and that is the whole problem.

What each account type actually does

Sync is not one mechanism. The account type determines how updates travel, how fast, and what gets left behind.

Account	How updates travel	Common reason nothing appears
iCloud	Pushed as changes happen	Calendars switched off for iCloud on one device
Google	Fetched on a schedule, or pushed	Calendar not selected for sync on Apple devices
Exchange	Pushed, subject to server policy	Account added for Mail only, not Calendars
On My Mac	Does not travel at all	Event written to a local calendar
Subscribed	Refreshed on an interval, read only	Interval set to a long period, or to manual

A subscribed calendar deserves a note of its own. Subscribed calendars are read only and refresh on a timer that is set per calendar, so a shared team calendar that looks stale is often working exactly as configured. Control click the calendar name, choose Get Info, and look at the Auto refresh menu.

The settings that fix most cases on the Mac

Start with the refresh interval, because it is the setting most often left at a value that makes a working account look broken. Choose Calendar then Settings, click Accounts, select the account, and open the Refresh Calendars menu. Apple documents this control directly.

If you choose Push, the account is updated automatically when you make a change on any of your devices that use the same account, or when someone makes a change to a shared calendar in that account. Source: support.apple.com

An account set to refresh every hour will be an hour behind, every time, and that is not a fault. Set it to Push where the account supports it. For a one off check, View then Refresh Calendars forces an immediate update.

Next, confirm the account is actually enabled for calendars rather than just present. In Calendar, choose Calendar then Accounts, select the account, and check that the Calendars checkbox is selected. Clearing that box hides every calendar in the account without removing the account, which produces the exact symptom of a phone that has events and a Mac that does not. The same screen is where an account is added, through Calendar then Add Account.

Finally, check the default calendar. Calendar then Settings then General has a Default Calendar menu. If it points at a calendar under On My Mac, every event created without thinking about it lands somewhere that cannot travel. Point it at the account that should own new events.

The settings that fix most cases on the iPhone

The phone has fewer places to look, and they are all in Settings rather than in the Calendar app.

For iCloud, open Settings, tap the name at the top, then iCloud, then see all apps, and confirm Calendars is on. Turning this off and on again is not a superstition here: switching it off removes iCloud calendars from the device, and switching it back on pulls a fresh copy from the account, which resolves a device that has fallen out of step.

For a Google or Exchange account, the account is listed under Apps then Calendar then Accounts. Open the account and confirm the Calendars toggle is on. An account added for Mail alone will show mail perfectly and no events at all, which reads as a calendar fault and is not one.

Two more checks matter on the phone. Background App Refresh affects how aggressively the device fetches on a schedule, and a Low Data Mode or Low Power Mode state can delay fetches until the device is on power or on a familiar network. If events arrive on the phone reliably but always late, look here rather than at the account.

Time zone is the last one. Calendar has a Time Zone Override setting on both platforms. When it is enabled on one device and not the other, events are correct but displayed at a shifted hour, which is a different bug from a missing event and needs a different fix. Deciding where an hour went is easier once travel and transitions are written into the day as real blocks rather than left implicit, which is covered in Travel time.

When only some Google calendars come through

This is the case that looks most like a broken sync and is almost always a configuration that was never set. Apple Calendar does not receive every calendar visible in a Google account. It receives a specific subset by default, and the rest have to be selected.

Which calendars are automatically synced: Any calendars that you find under "My Calendars" in Google Calendar on your computer. Birthdays. Source: support.google.com

Everything under Other Calendars, which is where shared team calendars, holiday calendars, and subscriptions collect, is excluded unless it is switched on from Google's Calendar sync page. Check the calendars that should travel, save, and then refresh in Apple Calendar. Until that is done, the calendar is not late, it was never requested.

Google also documents a short list of its own features that do not survive the trip: email notifications for events, creating new Google calendars, and the room scheduler. An event that reaches the Mac but silently loses its email reminder has not failed to sync. The reminder type does not exist on the other side.

One stale configuration blocks this entirely. If the Delegation tool was ever used in Apple Calendar to reach a Google account, it has to be switched off, in Calendar then Settings then Accounts then Delegation, before calendar sync will work at all.

Let the account's own view settle the argument

Comparing two devices to each other can only establish that they disagree. It cannot establish which one is right, and that matters, because the fix for a device that is missing an event is the opposite of the fix for a device that is holding an event nobody else has.

The account itself is the referee. Open the calendar in a browser: iCloud.com for an iCloud calendar, or Google Calendar on the web for a Google account. Whatever is there is what the account holds. Three outcomes, and each points somewhere different.

If the event is in the browser and missing on one device, that device is not receiving. The problem is on the receiving side, and the refresh interval, the account checkbox, and the per calendar visibility switches are where to look. Note that last one, because it is easy to miss. A calendar can be fully synced and simply unticked in the calendar list, in which case its events are present on the device and invisible.

If the event is missing in the browser but present on a device, that device never managed to send it. This usually means the event was created while the device was offline and the upload has not completed, or it was created in a local calendar that only looks like it belongs to the account. Opening the event and checking which calendar it names will say which.

If the event is in the browser and missing everywhere else, and it was created by someone else, check whether the invitation is still pending. An unanswered invitation behaves differently from an accepted event and may not be shown at all depending on the setting for showing declined and unanswered items.

Doing this check first turns an open ended problem into one of three narrow ones, and it takes under a minute. Working through settings without it means changing things on a device that was never at fault.

When events arrive but alerts do not

Events landing correctly while notifications stay silent is a separate problem with its own checklist, and troubleshooting sync will never fix it. Apple lists the places to look: alerts turned off in Calendar settings, notifications turned off for Calendar in System Settings, an active Focus, and event alert times set to None.

The Focus case is worth singling out because it is invisible. A Focus that was enabled once and never turned off will suppress calendar alerts indefinitely while every event continues to arrive on time, so the calendar looks healthy and the reminders are gone. Apple's page on alerts that do not appear runs through the rest.

There is also a limit worth knowing before blaming the account: an Exchange event can carry only one alert. Setting a second one on an Exchange calendar does not fail loudly, it simply does not take.

What to change first

Show the calendar list, find the heading above the calendar that holds the missing event, and fix the setting that belongs to that account type rather than working through a generic list. If the heading was On My Mac, change the default calendar before doing anything else, because every new event is still landing in a place that cannot travel. If events keep arriving in the wrong account because entering them is fiddly in the first place, the entry step is worth looking at, and Caltimate is built around that part.