Default is US date format : MM/dd/yyyy
Also, the login given default language will affect the dateformat. Sounds need to change both of them.
SQL server ref.: http://support.microsoft.com/kb/173907
SQL server express ref.: http://www.sqlservercentral.com/Forums/Topic1004359-146-1.aspx#bm1004496
EXEC sp_configure ‘default language’, ’23’ — british_english ?
GO
RECONFIGURE;