@Sokoban Thanks for posting in our Q&A.
Currently, there is no built-in setting in intune that can change Regional Format to 24 Hours. However, we can make it via Powershell script.
Write-Host "Setting Short time format"
Set-ItemProperty -Path "HKCU:\Control Panel\International" -name sShortTime -value "HH:mm"
Write-Host "Setting Long time format"
Set-ItemProperty -Path "HKCU:\Control Panel\International" -name sTimeFormat -value "HH:mm:ss"
We can deploy this script via intune. Please refer to the article:
https://learn.microsoft.com/en-us/mem/intune/apps/intune-management-extension
I have done the test in my lab. It works well. When I use an Azure AD account to sign in the device, the regional format is changed to 24 Hours.
Hope it will give you some ideas.
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