Original human_time_difference function; given a timestamp and optionally another, it will return the largest reasonable time differential between the two.

utility.php

	public static function human_time_difference($from, $to = '') {
		if ( empty($to) ) {
			$to = time();
		}
		
		$periods = array(
			'minutes' => array('%s minute', '%s minutes'),
			'hours' => array('%s hour', '%s hours'),
			'days' => array('%s day', '%s days'),
			'weeks' => array('%s week', '%s weeks'),
			'months' => array('%s month', '%s months'),
			'years' => array('%s year', '%s years')
		);
		$ranges = array(
			'years' => 31556926,
			'months' => 2592000,
			'weeks' => 604800,
			'days' => 86400,
			'hours' => 3600,
			'minutes' => 60
		);


		$diff = (int) abs($to - $from);
		$since = '';

		foreach ($ranges as $unit => $value) {
			
			if ( $diff <= $value ) continue;

			$time = round($diff / $value);
			if ( $time < 1 ) {
				$time = 1;
			}

			$since = sprintf(_n($periods[$unit][0], $periods[$unit][1], $time), $time);
			break;
		}


		return $since;
	}