topic Re: FormatDate for month abbreviation on Windows 11 24H2 works different in Product Forum

FormatDate for month abbreviation on Windows 11 24H2 works different

JoshuaKingsley — Thu, 10 Sep 2026 10:48:28 GMT

Hello everyone!

We noticed a very unusual behavior after upgrading some of our machines to Windows 11 24H2.

The expression FormatDate(Today(),"MMM") is returning "Sept" instead of the expected "Sep".

Useful Windows setting:

Edition: Windows 11 Enterprise

Version: 24H2

OS Build: 26100.9168

Windows Feature Experience Pack 1000.26100.344.0

Country or region: Belgium

Regional format: English (Belgium)

CultureInfo.CurrentCulture.Name = en-BE

CultureInfo.CurrentUICulture.Name = en-US

Thanks in advance.

Re: FormatDate for month abbreviation on Windows 11 24H2 works different

david.l.morris — Thu, 10 Sep 2026 13:15:14 GMT

As you probably determined, this is an intentional change that isn't caused by Blue Prism. It would affect any application using .NET to generate the abbreviation of months. Lots of people have gone through this outside of Blue Prism. Here is an example:
Why did Windows 11 24H2 update change English (New Zealand) AbbreviatedMonthName (MMM) for September from Sep to Sept? - Microsoft Q&A

In the very last reply on that thread, the person explains that it was an intentional change by Microsoft to align with standardized abbreviations. This is normal for Microsoft. They tend to take much longer than any other technology stack to adapt to some global/industry standard.

I would suggest embracing the new spelling. If it has broken any automations, then of course you can create your own object action to return the 'Sep' spelling, or specific automations reliant on it could take the first 3 letters or have a choice stage of its own to return Sep when the month is 9 or something like that.

Re: FormatDate for month abbreviation on Windows 11 24H2 works different

JoshuaKingsley — Thu, 10 Sep 2026 14:24:53 GMT

Hi Dave, thanks. I found the root cause after asking the same question to Copilot. I didn't expect them to make this kind of change. Yes, quite a few projects have already been affected, and I plan to replace it with a simple code stage.

topic Re: FormatDate for month abbreviation on ﻿Windows 11 24H2 works different in Product Forum

FormatDate for month abbreviation on ﻿Windows 11 24H2 works different

Re: FormatDate for month abbreviation on ﻿Windows 11 24H2 works different

Re: FormatDate for month abbreviation on ﻿Windows 11 24H2 works different

topic Re: FormatDate for month abbreviation on Windows 11 24H2 works different in Product Forum

FormatDate for month abbreviation on Windows 11 24H2 works different

Re: FormatDate for month abbreviation on Windows 11 24H2 works different

Re: FormatDate for month abbreviation on Windows 11 24H2 works different