Outlook calendar not syncing with Google? The 7 real reasons

Your Outlook calendar stopped showing up in Google, or the other way around. The usual advice — restart the app, check your connection, toggle the calendar off and on — almost never fixes it, because none of those is the actual problem. Here are the seven real reasons, roughly in order of how often we see them, including the ones that no setting will fix.

1. You’re not syncing — you’re subscribed to a snapshot

The most common “sync” between Outlook and Google isn’t sync at all. It’s an ICS subscription: one calendar publishes a URL, the other periodically downloads it. The official instructions from both Microsoft and Google set you up this way.

Two consequences. First, it’s read-only — changes flow in one direction, and accepting an event on the subscribed copy does nothing. Second, it’s slow on a schedule you don’t control. Google refreshes external ICS feeds roughly every 12–24 hours; Outlook refreshes subscribed calendars every few hours at best. There is no refresh button. If your “sync” shows yesterday’s calendar, this is why — and it isn’t broken. It’s working exactly as designed. The design is just not sync.

2. The subscription went stale and nothing told you

ICS URLs and account connections die quietly: a password change, a revoked token, an expired sharing link, an IT policy update on the publishing side. Neither Outlook nor Google shows an error for a feed that stopped updating — the events you already imported sit there looking plausible while nothing new arrives. If your calendar seems frozen at a date a few weeks back, unsubscribe and re-add the feed, and check whether the publishing account changed credentials around that date.

3. “New Outlook” changed the rules

Microsoft’s rollout of the new Outlook for Windows broke several Google-calendar workflows that had quietly worked for years. Connected Google calendars stopped displaying for some users; invite handling between Google accounts and new Outlook changed; and tools that depended on classic Outlook’s local data model — including Google’s own GWSMO sync tool — don’t work in new Outlook at all. If your sync broke around the time you switched (or were switched) to new Outlook, the switch is your cause. Workarounds exist case by case, but classic-Outlook-era plumbing is not coming back.

4. Classic Outlook + IMAP can’t see calendars at all

If your Gmail account is added to desktop Outlook via IMAP — the default for plain Gmail — you get mail only. IMAP carries no calendar data. People stare at settings for hours looking for the missing calendar checkbox; it doesn’t exist. Calendar data requires a different connection entirely (an ICS subscription, with the limits from reason #1, or a true sync service).

5. Invites get eaten in transit

A client books you from their Outlook; the invite never lands on your Google calendar. Three separate mechanisms can eat it: Gmail’s “only show invitations from known senders” setting (now the default on many accounts), malformed iCalendar attachments from some Exchange configurations, and new-Outlook invite routing quirks. The meeting exists on their side, nothing exists on yours, and no one gets an error. We wrote about the deeper version of this — events that vanish from an established sync — in why your Google–Outlook sync keeps dropping events.

6. Your sync tool’s plumbing expired

If you use an actual sync tool and it worked for weeks before going quiet, the likely culprits are infrastructure, not configuration: an expired OAuth token after a password change or an IT-forced reauthorization; a push-notification subscription that lapsed (Google’s and Microsoft’s both expire after days and must be renewed by the tool); or a sync token the provider invalidated, which a careless engine misreads as “nothing changed.” None of these produce a visible error on your calendar. A well-built engine renews subscriptions before they lapse, does a full re-sync when tokens are invalidated, and re-checks calendars on a schedule as a safety net precisely because it assumes some of this will fail.

7. Time zones and all-day events put things in the wrong place

Sometimes the event synced — to the wrong day. All-day events have a date but no time, and Google and Microsoft represent them differently; convert carelessly through a time zone and a birthday lands a day early, or an event near midnight slips outside the window a tool is checking and never appears. If your “missing” events cluster around all-day entries or late-night times, you’re looking at a conversion bug, not a connection problem.

What actually fixes it

Be honest about which case you’re in. If you just need a once-a-day glance at a second calendar, an ICS subscription is free and fine — know that it lags by hours and is read-only. If you’re technical and live on Windows desktop with classic Outlook, the open-source OGCS does real polling sync for free. But if you run your work from your calendar — if a stale or missing event costs you a meeting or a client — the requirement is real-time, two-way sync with infrastructure that renews itself and re-checks its own work.

That’s the product we build. twocal keeps Google, Microsoft, and Apple calendars in sync in seconds — and publishes its reliability on a public dashboard. $19/month flat for up to 15 calendars, 14 days free.