$('body').bind('onload, change', '.timer_input', function() {
      $('.tab-content .table_index').each(function() {
        $(this).find('.sum_total').text([].reduce.call(
            this.querySelectorAll('input.timer_input'),
            (res, node) => res + +(node.value || 0),
            0
        ));
      });
    }).change();

<ul class="nav nav-tabs">
  <li><a class="sum_total" data-toggle="tab" href="#Monday">04 Mar Monday 2.0</a></li>
  <li><a class="sum_total" data-toggle="tab" href="#Tuesday">05 Mar Tuesday </a></li>
  <li class="active"><a class="sum_total" data-toggle="tab" href="#Wednesday">06 Mar Wednesday 3.0</a></li>
  <li><a class="sum_total" data-toggle="tab" href="#Thursday">07 Mar Thursday </a></li>
  <li><a class="sum_total" data-toggle="tab" href="#Friday">08 Mar Friday </a></li>
  <li><a class="sum_total" data-toggle="tab" href="#Saturday">09 Mar Saturday </a></li>
</ul>

$('body').on('change', '.timer_input', function() {
    $('.tab-content .table_index').each(function() {
        const sum = [].reduce.call(
            this.querySelectorAll('input.timer_input'),
            (res, node) => res + +(node.value || 0),
            0
        );

        const id = $(this).find('.sum_total').text(sum).closest('.tab-pane').attr('id');

        $('a[href="#' + id + '"].sum_total').text(sum);
    });
}).change();