SQL SERVER DATETIME FORMAT

try this:

select convert(varchar, dob2, 101)
select convert(varchar, dob2, 102)
select convert(varchar, dob2, 103)
select convert(varchar, dob2, 104)
select convert(varchar, dob2, 105)
select convert(varchar, dob2, 106)
select convert(varchar, dob2, 107)
select convert(varchar, dob2, 108)
select convert(varchar, dob2, 109)
select convert(varchar, dob2, 110)
select convert(varchar, dob2, 111)
select convert(varchar, dob2, 112)
select convert(varchar, dob2, 113)

refernces: http://msdn.microsoft.com/en-us/library/ms187928.aspx

http://www.w3schools.com/sql/func_convert.asp

Compatibility Supports Says that Under compatibility level 110, the default style for CAST and CONVERT operations on time and datetime2 data types is always 121. If your query relies on the old behavior, use a compatibility level less than 110, or explicitly specify the 0 style in the affected query.

That means by default datetime2 is CAST as varchar to 121 format. For ex; col1 and col2 formats (below) are same (other than the 0s at the end)

SELECT CONVERT(varchar, GETDATE(), 121) col1,
       CAST(convert(datetime2,GETDATE()) as varchar) col2,
       CAST(GETDATE() as varchar) col3

SQL FIDDLE DEMO

--Results
COL1                    | COL2                          | COL3
2013-02-08 09:53:56.223 | 2013-02-08 09:53:56.2230000   | Feb 8 2013 9:53AM

FYI, if you use CONVERT instead of CAST you can use a third parameter to specify certain formats as listed here on MSDN

The default date format depends on the language setting for the database server. You can also change it per session, like:

set language french
select cast(getdate() as varchar(50))
-->
févr 8 2013 9:45AM

In MS SQL Server you can do:

SET DATEFORMAT ymd