— ok, Was a date format issue.  i used a European Date Format(dd-mm-yyyy) in my query but the system i use takes USA date Format(mm-dd-yyyy) so my query failed.
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- Solution
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    Select Cast(Case
    When EventDate <=’01/01/2016′ then ‘PreSeason’
    When EventDate >=’12/31/2016′ then ‘PostSeason’
    Else ‘Season’
    End As Varchar(25)) as Season, EventName From tblEvent
Thanks for Support!!!!
solved SQl CASE Statement