What version of windows and PowerShell are you running? I used to have this issue – and you can't change the UICulture – but on my Windows 10 machine with PowerShell 5.1 both cmdlets show en-GB as they should
I have Windows 7 Pro and Powershell 5. This problem is really causing chaos as all dates in Windows are dd/MM/yyyy so, for example, when I retrieve an environment variable (in PS) set to '13/10/20' I get "String was not recognized as a valid DateTim".
Is there maybe a Registry entry I can change?
From a quick google i found the following. The short version is that you change UICulture with the Language control panel, and Culture with the Region control panel. Culture just affects things like date / time / currency / number formats; UICulture is the actual language pack.
I agree; the problem being that everything is set to UK english in both of those places. I have done a temporary fix by adding a function to 'split' the date (reversing the Month/Day ones) before calling ToLongDateString() which works.