We had this problem in a dev environment the other day.  The developers decided to tell us after we’d installed and configured SQL and the SharePoint farm they needed to change the language settings of SQL because they were trying to input dates in dd/mm/yyyy (United Kingdom format), and by default SQL is setup with mm/dd/yyyy (US format).

It’s quite a simple fix, stop all SQL services, open up regedit and in the following areas change Language from 1033 to 2057 (decimal)

• HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\90\Tools\ClientSetup\CurrentVersion
• HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\90\Tools\Setup
• HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL.1\Setup
• HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQL.1\MSSQLServer\CurrentVersion

This will change the DEFAULT INSTANCE ONLY.  If you have other instances, change MSSQL.1 to MSSQL.2/etc for them.  To verify, run the following;

• SET Language British
• select @@Language, @@Langid

This should return the value British 23.  In the Properties of the SQL Instance in Management Studio, you will see;

English (United Kingdom)