Try like this
Load If(DateField1 < DateField2 , If(DateField1 < DateField3, 'DateField1 has minimum date','DateField3 has minimum date'),if(DateField2 <DateField3, 'DateField2 has minimum date','DateField3 has minimum date'));
Load min(DateField1) as DateField1 ,min(DateField2) as DateField2,min(DateField3) as DateField3 From Table where Year(DateField)=2012;
1) if your Date field is returning dates from DB in format such as 'DD/MM/YY hh:mm:ss TT' or 'DD/MM/YY' , try this
Year(Date(Trunc(Date_field),'DD/MM/YY') = '2012' or Year(Date(Date_field,'DD/MM/YY') = '2012'
2) Convert the Date field into number and use the min function, Min(num(Date#(Datefield,'format')))