IncreaseViewHelper.php

<?php
namespace AOE\SchedulerTimeline\ViewHelpers;

use TYPO3Fluid\Fluid\Core\ViewHelper\Traits\CompileWithRenderStatic;

/**
 * Class IncreaseViewHelper
 *
 */
class IncreaseViewHelper extends \TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper
{
    use CompileWithRenderStatic;

    protected $escapeOutput = false;

    /**
     * Render
     *
     * @param string $start
     * @param string $end
     * @param string $interval
     * @param string $iterator
     * @return string
     */
    public function render($start, $end, $interval = '1', $iterator = 'i')
    {
        $escapingEnabled = $this->isChildrenEscapingEnabled();

        $result = '';
        for ($i = $start; $i < $end; $i += $interval) {
            $this->templateVariableContainer->add($iterator, $i);
            $result .= $this->renderChildren();
            $this->templateVariableContainer->remove($iterator);
        }
        return $result;
    }
}

Timeline.html

<div class="row hours">
  <div class="timeline">
    <s:increase start="{starttime}" end="{endtime}" interval="3600">
      <div class="hour"><s:format.speakingDate timestamp="{i}" /></div>
    </s:increase>
  </div>
</div>

See tweet:
https://twitter.com/tomasnorre/status/1121350986457595904