calender_date_select

<td class="col-1">
         <div class="label-field-pair3">
        <div class="text-input-bg3">
        <%= exam_form.calendar_date_select :start_time %>
        </div>
        </div>
        </td>

Error:`@new[exams]' is not allowed as an instance variable name
wht shell i do .i have installed the gem also it is not working