Why a subscribed calendar isn't updating, and how long each app takes

The short answer

Your calendar app only sees changes when it downloads the subscribed calendar again, and each app picks its own timing. A change that shows up hours late means the link works and the app hadn't checked yet. AddEvent, which hosts subscription calendars, puts Google Calendar's checks at every 12 to 24 hours. Microsoft's estimate for Outlook.com is every 3 hours, though some changes take more than a day. On a Mac you set how often Apple Calendar checks, under Auto-refresh.

How often does each app check a subscribed calendar?

App	How often it checks	Can you change it?
Google Calendar	Every 12 to 24 hours, by AddEvent's estimate	No
Outlook.com	Every 3 hours by Microsoft's estimate, and sometimes more than 24	No
Outlook on the web, with a work or school account	Every 6 hours by Microsoft's estimate, and sometimes more than 24	No
Apple Calendar on a Mac	As often as its Auto-refresh setting says	Yes: Control-click the calendar, choose Get Info, then Auto-refresh
iPhone and iPad	On the device's own schedule, which Apple doesn't publish	Not directly

Why don't subscribed calendars update instantly?

A subscription is a link to a calendar file that the publisher keeps up to date. When the publisher changes something, nothing alerts your app. It has to download the file again, and it decides for itself how often to do that.

Calendar files can carry a suggested refresh interval from the publisher. Apps are free to ignore it.

Is it slow, or has the link stopped working?

Check that it's a subscription. If you downloaded a calendar file and opened it, or used an Import option, you have a copy of the events from that day, and Microsoft describes an import as a snapshot that won't update. Subscribed calendars get listed as a calendar of their own, under a heading like Other calendars or Subscribed. When the events sit in your main calendar instead, delete them and subscribe with the link.
Subscribe on a second app or device. If the new copy has the change, the link works and your first app hasn't checked since.
Make sure the calendar is ticked in the app's list of calendars, since an unticked one stays hidden. On a phone, check that the account holding it syncs calendars to that phone.
Refresh by hand where the app allows it. Apple Calendar on a Mac has View > Refresh Calendars. Google Calendar has no refresh button for a calendar added by URL, so remove it and add the link again to fetch it fresh.
Ask the publisher for the current link if it still never changes. Links get replaced and switched off.

Google Calendar on the web: the add button next to Other calendars, with From URL in its menu — In Google Calendar on the web, subscribed calendars go in under Other calendars, From URL.

An event shows at the wrong time

If it's off by a whole number of hours, look at time zones. Check the time zone on the device and in the calendar app's settings. When both are right, send the publisher the event's name and the time you see.

Why is a subscribed calendar missing on my iPad or my other Mac?

If you subscribed in Apple Calendar on a Mac, check where the subscription was saved, since one kept On My Mac stays on that Mac. A Location menu asks as you subscribe, and Apple's guide spells out the choice: “If you choose your iCloud account, the calendar is available on all your computers and devices that are set up with iCloud. If you choose On My Mac, the calendar is saved on your computer.”

To get it on your other devices, subscribe again on the Mac and choose iCloud under Location. Then Control-click the old copy in the calendar list and choose Unsubscribe. On an iPhone or iPad, Apple's steps for iCloud calendar subscriptions have you pick iCloud as the account when you add one, and Apple says to “sign in to iCloud with the same Apple Account on all of your devices.”

What if changes can't wait?

The delay matters most when plans change on the day. Say rain pushes the member-guest back two hours. Google can take a day to pick that up, and members who check their phone could show up at the original time.

Events that need to change fast have to go straight into people's calendars through their Google or Microsoft account, with their permission, and then a change reaches their copy of the event within moments. Our guide to “Add to calendar” buttons and subscriptions walks through the options.

How TheyCal handles this

We make TheyCal, and these refresh times shaped how it works. When someone follows a business on Google or Microsoft, we ask them to connect their calendar so we can create and update events in it directly. Apple Calendar users and people on other apps get a private calendar link. Each link suggests an hourly refresh to the app that subscribes to it.

Common questions

How do I make Google Calendar refresh a subscribed calendar faster?

You can pull the latest version once by removing the calendar and adding the link again. After that Google goes back to its own schedule, which AddEvent puts at every 12 to 24 hours.

Does Outlook have a setting for how often subscribed calendars update?

Microsoft sets the timing itself. It estimates every 3 hours for Outlook.com and every 6 for Outlook on the web with a work or school account, and says some changes take more than 24.

Why did events disappear from my subscribed calendar?

A subscribed calendar mirrors what the publisher's calendar holds right now. Cancelled events drop out at the next refresh, and so do old ones when the publisher only shares upcoming and recent events. If every event vanished at once, ask the publisher whether they replaced the link.

Can I edit events in a subscribed calendar?

Subscribed calendars are read-only. You can hide one or unsubscribe.