A client of mine recently ran into a problem with Cognos Data Manager using the newer SQL Server date/time format called datetime2. It is an extension of the original date/time format of SQL Server and is in all versions of SQL Server from 2008 and up. Datetime2 is incompatible with Cognos Data Manager, at least as it pertains to calculations. Data Manager will process datetime2 dates as long as they are not manipulated or used in calculations. However, if they are, you will need to cast them as the original datetime data type. Cognos Data Manager will otherwise treat them as an unrecognized data type and fail the Data Manager jobs.
This is a fairly easy workaround, but it is something to be careful about when you are using Cognos Data Manager and interfacing with SQL Server 2008, SQL Server 2008 R2 or SQL Server 2012.