How to Fix Outlook Calendar Taking a Long Time to Sync Error?

Approved By Anuraag Singh

Published On June 29th, 2026

Reading Time 7 Minutes Reading

Category ICS

Is your Outlook calendar taking a long time to sync? The slow syncing of your calendar may cause you to miss appointments, duplicate events, and manage it improperly, especially for those who use Microsoft Outlook on a regular basis. If the calendar does not sync instantly or gets stuck while syncing, there might be many reasons behind this issue, including network problems, large size of your calendar, corruption in the cache file, or corruption in the ICS file. Here, you will learn how to resolve Outlook Calendar sync issues using both manual and automated solutions.

Common Reasons Why Outlook Calendar Taking a Long Time to Load

Before moving to the solution to resolve Outlook Calendar taking a long time to sync error. We have mentioned some of the common reasons on why this issue occurs:

Internet connection problems or unstable connection: Outlook needs a stable connection to exchange information with the server, either Microsoft Exchange or Microsoft 365. The process will be delayed if the internet connection is interrupted by any means like frequent switching from Wi-Fi to mobile data or vice versa.
Corrupted OST/PST file: The OST or PST files contain mailbox information. If these files get corrupted due to any reason like unexpected shutdown or sync problem, then there could be problems with accessing calendar information.
Damaged Outlook Profile: An Outlook profile holds settings for the user’s account and synchronization. In case the profile gets misconfigured or damaged, the application may experience difficulties synchronizing calendar events effectively, causing recurring problems with the process.
Problematic add-ons: There are some third-party add-ons that affect the normal functioning of Outlook. Some get into the system resources while others conflict with the calendar synchronization function causing Outlook Calendar taking a long time to sync error.
Corrupted calendar cache: The application stores cached copies of calendar data locally in order to improve the access to this data. In case this cache gets corrupted or outdated, the application will need more time to update it or verify data.
Several synchronized calendars: If several calendars are synchronized simultaneously, there will be more data that will have to be processed by Outlook.
Older versions of Outlook application: The old versions of the Outlook application might have issues that could cause problems during the syncing of calendar data. When outdated software is used without updating, then there will be problems when syncing the calendar data.
Large ICS Files: Large ICS calendar files might slow down the Outlook application when they are imported into the program due to their large size and the complexity of their calendar data.

Method 1: Check the Internet Connection

When your Outlook Calendar is taking a long time to sync, check that Outlook has a connection to the internet. The steps to fix Outlook Calendar taking a long time to sync error using this method are as follows:

Firstly, open the Browser in your device
Then, visit the multiple websites and restart your router
After that, switch to another network if possible
Next, disable the VPN temporarily
At last, reopen the Outlook application

Also Read: How to Fix iPhone Calendar Not Syncing with MacBook?

Resolve Outlook Calendar Taking a Long Time to Sync through Update Microsoft Outlook Option

Using an outdated versions of Microsoft Outlook can also cause syncing problems. So it is important to update the Outlook applications. The steps to update the application are as follows:

Firstly, open the Outlook application
Then, click on the file option and choose Office Account
After that, tap on the update options and choose update now
Then, install the available updates and restart the Outlook application

Method 3: Fix the Outlook Error Using Disable Unnecessary Outlook Add-ins Feature

Sometimes, the third-party add-ins in the Outlook application may interfere with the synchronization. Follow the steps to remove and disable these unnecessary add-ins to resolve Outlook Calendar taking a long time to sync issue:

Firstly, open the Microsoft Outlook application
Then, navigate to the file > options > Add-ins
After that, choose the COM add-ins and tap the Go button
Then, disable the unnecessary add-ins
After that, restart the Outlook application

Method 4: Repair the Outlook Data File

Corruption in OST or PST files can slow the Outlook synchronization process, so repairing the damaged files can fix the Outlook Calendar taking a long time to sync error. The steps are:

Close the Outlook application
Then, locate the SCANPST.EXE
Now, launch the inbox repair tool
Then, browse the PST file
After that, click on the start button
Then, repair the detected errors
Now, open the Outlook again

Method 5: Resolve Outlook Calendar Taking a Long Time to Sync Issue Professionally

Synchronization issues can arise when the problem is linked to the large ICS calendar files in Microsoft Outlook. When there is too much data in the ICS file in terms of thousands of calendar entries, Outlook may have difficulty importing and synchronizing this file. Using SysTools ICS Splitter Software will be very helpful in such scenarios. Rather than manually working on large ICS files, this software helps break down large ICS files into several small files based on various criteria such as size, dates, and event counts. etc. The interface of the tool is simple and easy to use for both technical and non technical users.

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Working Steps of the Software

Download and Run the aforementioned tool, then choose the split ICS file option.
Then, click on the Add file or Add folder to upload the ICS file.
To fix Outlook Calendar taking a long time to sync, choose the splitting options.
After that, you will get a window prompt that the Split process completed successfully. Hit the “OK” button.
Now, tap on the view report option to view the process report.

Why Choose Automated Solution over Manual Methods?

Below, we have given the comparison table highlighting the key differences between the manual and automated solutions. This table will help you choose the right method to fix Outlook Calendar taking a long time to sync error.

Features	Manual Methods	Automated Tool
Ease of Use	Requires multiple troubleshooting steps and technical knowledge	Simple, automated process with an intuitive interface
Handling Large ICS File	Manual splitting is time-consuming and prone to errors	Automatically splits large ICS files without data loss
Bulk Processing	Not supported	Supports splitting multiple ICS files in one go
Data Integrity	Risk of losing or modifying calendar data during manual editing	Preserves all calendar events, recurring meetings, reminders, and metadata
Time Efficiency	Requires significant manual effort and troubleshooting	Fast, automated solution that saves time and improves Outlook performance

Final Thoughts

In this guide, we have covered how to fix Outlook Calendar taking a long time to sync error. We have discussed the common reasons on why this issue occurs. Furthermore, we have mentioned both manual and automated solutions to resolve this Outlook Calendar issue. The manual methods will help in the basic sync process, whereas for large calendar files, we have suggested you to use the professional solution.