Try this with simply replace,
<% @employees = Employee.where("status = ? AND strftime('%d/%m', date_of_birth) = ?", "Active" , date.strftime('%d/%m')) %>
With
<% @employees = Employee.where("status = ? AND DATE_FORMAT(date_of_birth,'%d/%m') = ?", "Active" , date.strftime('%d/%m')) %>
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