After moving mailbox’s from Exchange 2003 to 2010, one remote user reported their OWA was in Spanish.
This can be fun to try and walk them through changing the OWA language options over the phone when the options are in spanish so I opted to fix it via the Exchange Management Shell:
[PS] C:\Windows\system32>Set-MailboxRegionalConfiguration -Identity jsmith -Language en-us
[PS] C:\Windows\system32>get-mailboxregionalconfiguration -identity dlogsdon |fl
RunspaceId : 8d5eecb9-1952-4605-876f-c08c540d96a8
DateFormat : M/d/yyyy
Language : en-US
DefaultFolderNameMatchingUserLanguage : False
TimeFormat : h:mm tt
TimeZone : Pacific Standard Time
Identity :
IsValid : True
Alternatively, you can change the setting via Outlook Web Access: