How to fix Outlook calendar events showing the wrong duration or end time after editing in Microsoft 365

Calendars & Scheduling KB-555

Summary

This guide helps you troubleshoot and resolve: How to fix Outlook calendar events showing the wrong duration or end time after editing in Microsoft 365. Follow the steps below to fix the issue.

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Common Causes

Outlook calendar events in Microsoft 365 can occasionally display incorrect durations or end times after being edited, moved, or synced between devices. This commonly occurs when time zones are inconsistent across devices, when events are edited on a mobile app before syncing back to the desktop client, or when cached calendar data conflicts with the server. The steps below will help you resolve the issue and prevent it from recurring.

Quick Fix Steps

Try these steps first — they resolve the issue in most cases:

Close Outlook on all devices.
Open Outlook on the web (outlook.office.com) and verify the event shows the correct time there.
Reopen Outlook on your primary device and let it fully sync.
If the issue persists, clear the Outlook cache and resync your calendar.

Detailed Instructions

Step 1: Verify the Event in Outlook on the Web

The web version of Outlook is always in sync with the server, so it shows the source of truth. Before making changes elsewhere, confirm whether the problem exists there too.

Open a browser and go to outlook.office.com.
Sign in with your Microsoft 365 account.
Select the Calendar icon from the left navigation pane.
Open the affected event and note the Start, End, and Time zone fields.

If the event shows the correct duration in Outlook on the web but is wrong in your desktop or mobile app, the issue is local to that device and can be fixed by clearing the cache (see Step 3).

Step 2: Check Time Zone Settings on Every Device

Mismatched time zones are the most common cause of events shifting by hours after editing. Each device and each Outlook profile must use the correct time zone.

In Outlook on the Web

Select the Settings gear icon in the top right.
Choose View all Outlook settings.
Go to Calendar > View options.
Confirm the Time zone is set correctly for your location (for example, (UTC+10:00) Canberra, Melbourne, Sydney).
Select Save.

In Outlook for Windows

Select File > Options > Calendar.
Scroll to Time zones.
Tick Show a second time zone in Day/Week/Month view if you need to compare zones, otherwise leave it unticked.
Set the Time zone field to your local Australian time zone.
Untick Adjust for daylight saving time automatically only if your organisation requires fixed UTC offsets.
Select OK and restart Outlook.

In Outlook for Mac

Select Outlook > Settings (or Preferences).
Choose Calendar.
Set the Time zone to your local Australian zone.
Close Settings and restart Outlook.

In Outlook Mobile (iOS and Android)

Open the Outlook app and tap your profile icon.
Tap the Settings gear.
Tap Calendar.
Confirm the time zone matches your device's region setting.

If your devices show different time zones, Outlook will convert event times when syncing, which can shift the start or end of an event by one or more hours. Always align these settings before editing events.

Step 3: Clear the Outlook Cache

Stale cached calendar data can cause Outlook to display old or incorrect event durations even after the server has been updated. Clearing the cache forces Outlook to download fresh data.

Outlook for Windows

Close Outlook completely.
Press Windows + R, type %localappdata%\Microsoft\Outlook\RoamCache, and press Enter.
Select all files in the folder (Ctrl + A) and delete them.
Restart Outlook. It will rebuild the cache automatically.

New Outlook for Windows

Select the Settings gear in Outlook.
Go to General > About.
Choose Reset > Reset all settings.
Confirm and sign back in.

Outlook for Mac

Quit Outlook.
Open Finder, press Cmd + Shift + G, and enter ~/Library/Containers/com.microsoft.Outlook/Data/Library/Caches.
Move the contents of the cache folder to the Trash.
Restart Outlook.

Step 4: Recreate the Affected Event

If a single event continues to display the wrong duration after caching and time zone checks, the event itself may contain corrupted metadata. Recreating it is often the fastest fix.

In Outlook on the web, open the affected event.
Select Cancel > Send cancellation to attendees if attendees need to be notified, or choose Delete the meeting if it is personal.
Create a new event with the correct start, end, and time zone.
Re-invite any attendees from the new event.

Recreating the event is generally cleaner than trying to repair a single corrupted entry, especially for recurring meetings where one occurrence has drifted.

Step 5: Prevent the Issue From Returning

Edit calendar events on the same device whenever possible, or wait for sync to complete before switching devices.
Keep time zone settings consistent across every device that accesses your Microsoft 365 calendar.
Avoid editing events while Outlook is offline — changes made offline can conflict with server-side updates when you reconnect.
Update Outlook regularly so you have the latest sync and time zone fixes from Microsoft.

Troubleshooting

The Event Still Shows the Wrong Duration After All Steps

Open the event in Outlook on the web and check whether the Show as status is set to Free, Busy, Tentative, or Out of Office. Some custom forms override default duration behaviour.
Check whether the event is part of a recurring series. Editing a single occurrence can sometimes detach it from the series and cause duration drift. Right-click the event and choose Open the series to verify.
Confirm your mailbox is not full. A full mailbox can prevent calendar sync from completing, leaving Outlook to display cached event data.
Test from a second user account on the same device. If the issue only affects one mailbox, the problem is server-side and may require a Microsoft 365 admin to reset the calendar.

Events Shift by Exactly One Hour

A one-hour shift typically indicates a daylight saving time transition that Outlook has not applied correctly. Verify each device's time zone setting includes automatic DST adjustment, then recreate the affected events.

Events Shift by Several Hours

A multi-hour shift almost always points to a time zone mismatch between devices. Re-check the settings in Step 2 on every device that connects to your calendar.

You Suspect a Server-Side Issue

If the event shows the wrong duration in Outlook on the web as well, the problem is likely stored on the server. In this case:

Contact your Microsoft 365 administrator and ask them to run a mailbox repair using the Microsoft Support and Recovery Assistant.
Provide the administrator with the event subject, date, and time so they can locate the affected item.
Ask the administrator to check the message trace and sync logs for any errors related to your mailbox.

If you are part of a managed Microsoft 365 organisation, do not run the Microsoft Support and Recovery Assistant without checking with your IT administrator first — it can reset profile settings that affect other services.

Still Having Issues?

Need more help? If the issue persists after trying these steps, please open a support ticket and our team will assist you.

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