When Google Calendar is not syncing to Outlook, the cause is usually the refresh schedule: Outlook checks a subscribed Google Calendar about every 3 hours in Outlook.com and about every 6 hours in Outlook on the web, and either can take more than 24 hours. A Google Calendar imported into classic Outlook as an .ics file is a static snapshot that never updates, and an Outlook calendar added to Google Calendar by URL refreshes on a schedule Google does not publish. Re-subscribing repairs a broken link but does not shorten the wait, so to move changes faster, connect both calendars to a sync service such as Keeper.sh, a managed calendar sync service.
How often Outlook refreshes a Google Calendar subscription
Outlook pulls a subscribed calendar on Microsoft's schedule, not when Google Calendar changes. Microsoft gives a different interval for each client on its import and subscribe help page (checked 29 October 2026):
- Outlook.com: updates approximately every 3 hours.
- Outlook on the web: updates approximately every 6 hours.
- Either client: an update can take more than 24 hours.
Microsoft's own sharing documentation adds that with an ICS subscription, the receiving calendar service, not the calendar owner, chooses when to fetch new updates. Outlook has no button that makes a subscribed Google Calendar refresh sooner. An event you created in Google Calendar ten minutes ago will not be in Outlook yet, and that is expected behaviour rather than a fault. If nothing has arrived after a full day, the subscription itself is probably broken, which the section on stale subscriptions below covers.
Classic Outlook imports are a static snapshot
A Google Calendar brought into classic Outlook through File > Open & Export > Import/Export is a copy, not a connection. Microsoft's Google Calendar in Outlook page (checked 29 October 2026) says the imported calendar is a static snapshot that does not self-update. Its import-or-subscribe page says the same of any imported .ics file: Outlook does not refresh imported events, even when the calendar's owner changes them.
So an imported Google Calendar shows every event as it stood on the day of the import and nothing after. Microsoft gives two ways out: subscribe to the calendar instead, or repeat the import each time you want a fresh copy. In new Outlook, the subscription route is Add calendar > Subscribe from web, using the Google address described in the next section. Removing the imported copy first avoids seeing each event twice. The full subscription walkthrough is in the guide to adding Google Calendar to Outlook.
Fixing a stale or empty Google subscription in Outlook
A subscription that has shown no changes for more than 24 hours, or shows no events at all, usually points at the wrong Google address or one that no longer works. Check these in order:
- Use the secret address. Microsoft's subscribe steps use the Secret address in iCal format, found in Google Calendar under the calendar's settings, then Integrate calendar (Google Calendar help, checked 29 October 2026).
- Check whether the address was reset. Google's Reset button invalidates the old secret address and creates a new one, so an Outlook subscription still using the old address stops receiving events.
- Subscribe again with the current address. Remove the stale subscription in Outlook and add a new one with the secret address Google shows today.
- Allow the documented window. After subscribing, give Outlook.com about 3 hours and Outlook on the web about 6 hours before treating it as broken.
If Outlook is not updating any calendar, including its own Microsoft 365 or Outlook.com calendar, the fault is in the Outlook client or mailbox rather than the Google subscription. The Outlook calendar troubleshooting guide covers that resync.
When Outlook changes don't reach Google Calendar
The reverse direction is slower and less predictable, because Google Calendar decides when to fetch an Outlook calendar and publishes no refresh interval. An Outlook or Microsoft 365 calendar reaches Google Calendar as a published ICS link added through Other calendars > From URL. Google's add-by-URL help page (checked 29 October 2026) documents that route only for Google Calendar on a computer, gives no refresh timing, and notes that a calendar added by link has to be public.
Microsoft fills the gap on its calendar sharing in Microsoft 365 page: when the recipient is on Gmail, the shared calendar might update only every 24 to 48 hours. A meeting added in Outlook this morning can therefore stay missing from Google Calendar until tomorrow or the day after, with nothing to fix on either side. If an Outlook calendar has never appeared in Google Calendar at all, check that it is still published and that the link was added in full; the steps for both are in the guide to syncing Outlook Calendar to Google Calendar.
Syncing events directly instead of waiting on a subscription
Every native route above is a subscription, so the receiving calendar sets the pace and neither side can speed it up. A sync service avoids that by reading the source calendar and writing events into the destination calendar itself. Keeper.sh, a managed calendar sync service, connects Google Calendar to Outlook and Microsoft 365 this way: connect both accounts, choose the destination calendar, and Keeper.sh keeps them in sync.
- What Keeper.sh writes: a busy block named after the source calendar. Title, description and location are hidden by default, Pro can turn them back on per calendar, and guest lists are never copied.
- Direction: each connection runs one way. Add the reverse connection for Outlook changes to reach Google Calendar as well.
- Timing: on the Free plan, changes land every 30 minutes. On the Pro plan, Google and Outlook changes arrive within seconds.
Because the busy blocks are ordinary events in the destination calendar, they appear in Outlook and Google Calendar like any other event, with no subscription refresh involved. Both directions are set up in the guide to syncing Google Calendar with Outlook.