Can the default minimum date range for 'datetime' be changed in SQL Server 2008 R2?
A datetime2 goes back further - http://msdn.microsoft.com/en-us/library/bb677335.aspx - to 0001. If you want to go back further still, then a custom data type may be an option, although given the potential confusion and lack of precision even before 1753, it is doubtful how precise you could expect to be.