Either Microsoft Programmers or Defaults.
In the CAST and CONVERT (TSQL) BOL article there is a table with formats. My date is returned as the following if Management Studio query window withput formatting:
according to the table, the format name and description for that are:
ODBC canonical (with milliseconds)
It is not just default:
Default mon dd yyyy hh:miAM (or PM)
My assumption that it may be a front end (Management Studio) programmers formatted it this way because of 2 things:
1. When I use Profiler to profile running a query in Management Studio, the Profiler shows the original query, so the formatting is done in the front end.
2. Linked Server to Oracle query returnes dates /times in the same format as when running a query towards SQL Server.