Connect-ExchangeOnline
Set-MailboxRegionalConfiguration -Identity “user@domain.tld” -Language de-DE -DateFormat $null -TimeFormat $null -LocalizeDefaultFolderName
Connect-ExchangeOnline
Set-MailboxRegionalConfiguration -Identity “user@domain.tld” -Language de-DE -DateFormat $null -TimeFormat $null -LocalizeDefaultFolderName