Why do those Update statements fail using a datetime format? Given: 

Query #1:

begin tran
UPDATE [dbo].[t] SET [mydatetime]='2011-12-25 07:00:00.000';
rollback


Query #2: (changing month/day) 

begin tran
UPDATE [dbo].[t] SET [mydatetime]='2011-25-12 07:00:00.000';
rollback


Why does the QUERY #1 fail to run on a new installed SQL Server while query #2 runs succesfully? 


  Msg 242, Level 16, State 3, Line 6 Bei der Konvertierung eines
  varchar-Datentyps in einen datetime-Datentyp liegt der Wert außerhalb
  des gültigen Bereichs.


In comparison why does Query #1 run on the old server while query #2 fails on the new server?


  Msg 242, Level 16, State 3, Line 7 The conversion of a varchar data
  type to a datetime data type resulted in an out-of-range value.


The servers have different versions (2008 / 2016). And as you can see from error messages there are two different languages installed. Please don't tell me just because the language of the Sql-Server installation is different it is not able to handle different date formats?

Is this configurable?
Will I get away with uniform formats like 20150129 08:00:00.000 ?
You could deal with the issue by specifying the style and doing an explicit CONVERT() from string to datetime rather than an implicit conversion. https://msdn.microsoft.com/en-us/library/ms187928.aspx

UPDATE dbo.t SET mydatetime = CONVERT('2011-12-25 07:00:00.000', 121)