Why Excel Keeps Change Output Of and How to Fix It

If your workflow is blocked, confirm the account and app context, then follow the ordered fixes below.

Problem Description: Microsoft Change Output Of

Did Microsoft change the output of text(date,"yyyy-mmm") for September to become "yyyy-Sept", from the original "yyyy-Sep"? It has caused a lot of my excel files not working anymore because I have been naming a lot of tabs and so on by 'yyyy-Sep'. Seems there is no way I can have a quick fix other than amending all the formulassssss..... :'(

Quick Answer for Office Setup on New Device

The change from "Sep" to "Sept" in the TEXT function output for September is tied to a recent Windows or Microsoft 365 update that altered the short date format in certain regional settings, such as English-United Kingdom.

Likely Causes Behind Formula Errors Root Factors

• The Microsoft account or license context may not match the purchase or device.

• Cached credentials, outdated builds, or damaged local components can trigger formula errors.

• A file-specific corruption or add-in conflict can mimic a broader application failure.

Recommended Solution: Repairing Office Startup Issues

When to use this: Apply these steps when the symptoms match and you can access the relevant Microsoft account or administrator.

1. To revert to "Sep", provide details about your Excel version, regional settings, and any specific templates or settings in your files to help narrow down the cause.

Alternative Solutions for Secondary Excel Fixes

1. Test the same action in a private browser session or a new blank file to isolate account vs file issues.

2. Capture exact error text and screenshots before contacting Microsoft Support or your administrator.

Working with WPS Office: WPS as a Local Alternative

WPS Office cannot replace Microsoft account, activation, or cloud fixes for this scenario. It remains one of the best free Microsoft Office-compatible alternatives for opening and editing local files.

1. Download and install WPS Office from the official website.

2. Open local Word, Excel, PowerPoint, or PDF files in the matching WPS app.

3. Save a working copy locally while Microsoft-side issues are resolved.

4. Return to Microsoft Office after the primary fix succeeds.

If you need a practical local workspace in the meantime, try WPS Office.

Prevention Tips for Keeping Office Stable Long Term

• Keep one primary Microsoft account for subscriptions and Office sign-in.

• Install updates for Office and Windows before retrying failed workflows.

• Back up important files before repair, reset, or reinstall actions.

• Document exact error messages before the next troubleshooting attempt.

FAQs About Office Support Questions

Can WPS Office fix this formula errors issue directly? Only when the WPS steps match the formatting or file task. Account, activation, and cloud issues stay on the Microsoft side.

Should I reinstall Office before trying these steps? Not first. Confirm account, license, and the exact error before reinstalling.

What should I send to Microsoft Support? The affected account email, device type, Office version, exact error text, and screenshots with personal data hidden.