As of now, the dates for 2018 session is not released but as per previous year information the online regsitration will be starting in the month of February and it should be over in the month of March itself. Also, the test should be held in the month of May as last year it happened on 14th-May. Apart from this, you can go through the below provided link to know the syllabus and previous year papers for B.Math -

ISI B.Math Sample Papers

Hope this helps