locallang.xml

<?xml version="1.0" encoding="utf-8" standalone="yes" ?>
<T3locallang>
  <meta type="array">
		<type>database</type>
		<description>Language labels</description>
	</meta>
	<data type="array">
		<languageKey index="default" type="array">
			<label index="timespan.day">%d day</label>
			<label index="timespan.days">%d days</label>
			<label index="timespan.hour">%d hour</label>
			<label index="timespan.hours">%d hours</label>
			<label index="timespan.minute">%d minute</label>
			<label index="timespan.minutes">%d minutes</label>
			<label index="timespan.month">%d month</label>
			<label index="timespan.months">%d months</label>
			<label index="timespan.second">%d second</label>
			<label index="timespan.seconds">%d seconds</label>
			<label index="timespan.since">%s ago</label>
			<label index="timespan.until">in %s</label>
			<label index="timespan.year">%d year</label>
			<label index="timespan.years">%d years</label>
		</languageKey>
		<languageKey index="de" type="array">
			<label index="timespan.day">% Tag</label>
			<label index="timespan.days">% Tagen</label>
			<label index="timespan.hour">% Stunde</label>
			<label index="timespan.hours">% Stunden</label>
			<label index="timespan.month">% Monat</label>
			<label index="timespan.months">% Monaten</label>
			<label index="timespan.second">% Sekunde</label>
			<label index="timespan.seconds">% Sekunden</label>
			<label index="timespan.since">vor %</label>
			<label index="timespan.until">in %</label>
			<label index="timespan.year">% Jahr</label>
			<label index="timespan.years">% Jahren</label>
		</languageKey>
	</data>
</T3locallang>

TimeSpanViewHelper.php

<?php

namespace Smichaelsen\MyExt\ViewHelpers;

use TYPO3\CMS\Extbase\Utility\LocalizationUtility;
use TYPO3\CMS\Fluid\Core\ViewHelper\AbstractViewHelper;

/**
 * Class TimeSpanViewHelper
 *
 * Returns a human readable string stating the time interval between now and the given reference time.
 * Uses the locallang.xml/xlf of $this->extensionName. The LLL keys are:
 * timespan.day
 * timespan.days
 * timespan.hour
 * timespan.hours
 * timespan.minute
 * timespan.minutes
 * timespan.month
 * timespan.months
 * timespan.second
 * timespan.seconds
 * timespan.since
 * timespan.until
 * timespan.year
 * timespan.years
 *
 * Usage: <m:timeSpan reference="{myTime}" />
 * Example output: 4 days 12 hours 7 minutes and 42 seconds ago
 * Example output: in 4 days 12 hours 7 minutes and 42 seconds
 *
 * TODO: make it possible to use a specific precision. e.g. precision="minutes" won't include the seconds in the output
 *
 * @package Smichaelsen\MyExt\ViewHelpers
 */
class TimeSpanViewHelper extends AbstractViewHelper{

	/**
	 * @var string
	 */
	protected $extensionName = 'MyExt';

	/**
	 * Initialize the arguments.
	 *
	 * @return void
	 * @api
	 */
	public function initializeArguments() {
		parent::initializeArguments();
		$this->registerArgument('reference', 'DateTime', 'The reference time', TRUE);
	}

	/**
	 * return string
	 */
	public function render() {
		$messageParts = array();
		$now = new \DateTime();
		/** @var \DateTime $reference */
		$reference = $this->arguments['reference'];
		$difference = $now->diff($reference, TRUE);
		$timeunits = array(
			'year' => $difference->y,
			'month' => $difference->m,
			'day' => $difference->d,
			'hour' => $difference->h,
			'minute' => $difference->i,
			'second' => $difference->s,
		);
		foreach ($timeunits as $label => $value) {
			if ($value) {
				$messageParts[] = LocalizationUtility::translate('timespan.' . $label . ($value > 1 ? 's' : ''), $this->extensionName, array($value));
			}
		}
		return LocalizationUtility::translate('timespan.' . ($now > $reference ? 'since' : 'until'), $this->extensionName, array(join(' ', $messageParts)));
	}

}

?>