Date.php

<?php

class date {

	/**
	 * Display the time from now in a readable way
	 * @param int $targetTime
	 * @param int $now
	 * @return string
	 */
	static function fromNow($targetTime=0, $now=null) {
		if (!$now) {
			$now = time();
		}
		$seconddiff = $now - $targetTime; // Raw time difference
		$yeardiff = date('Y', $now) - date('Y', $targetTime);
		$datediff = self::countDays($now, $targetTime);
		
		//if the target is within 30 minutes, it is now
		if (abs($seconddiff) <= 60 * 30) {
			return 'Now';
		}
		
		//if the date is within a day
		elseif (abs($datediff) <= 1) {
			if ($datediff == 0) {
				return 'Today @ ' . date('H:i', $targetTime);
			} elseif ($datediff == -1) {
				return 'Yesterday @ ' . date('H:i', $targetTime);
			} else {
				return 'Tomorrow @ ' . date('H:i', $targetTime);
			}
		}
		
		//it is within the week, display that date as [day of the week] @ [hour]:[minute]
		elseif($datediff > 1 && $datediff <= 6){
			return date('D j @ H:i', $targetTime);
		}

		//otherwise, display the date as [Month] @ [hour]:[minute]
		else {
			return date('M j @ H:i', $targetTime);
		}
	}

	/**
	 * Count the number of days between the two timestamps
	 * @param int $fromTimestamp
	 * @param int $toTimestamp
	 * @return int
	 */
	public static function countDays($fromTimestamp, $toTimestamp) {
		// First we need to break these dates into their constituent parts:
		$fromDate = getdate($fromTimestamp);
		$toDate = getdate($toTimestamp);
		// Now recreate these timestamps, based upon noon on each day
		// The specific time doesn't matter but it must be the same each day
		$fromTime = mktime(12, 0, 0, $fromDate['mon'], $fromDate['mday'], $fromDate['year']);
		$toTime = mktime(12, 0, 0, $toDate['mon'], $toDate['mday'], $toDate['year']);
		// Subtract these two numbers and divide by the number of seconds in a
		// day. Round the result since crossing over a daylight savings time
		// barrier will cause this time to be off by an hour or two.
		return round(($toTime - $fromTime) / 86400);
	}
}

DateTest.php

<?php

require_once 'PHPUnit/Framework.php';

require_once dirname(__FILE__) . '/../date.php';

/**
 * Test class for date.
 * Generated by PHPUnit on 2010-08-18 at 19:22:49.
 */
class dateTest extends PHPUnit_Framework_TestCase {
	protected $now = null;
	/**
	 * @var date
	 */
	protected $object;

	protected function setUp() {
		//now == Jan 1 2010
		$this->now = mktime(0, 0, 0, 1, 1, 2010);
		$this->object = new date;
	}

	public function testFromNowYesterday() {
		$tests = array(
			'Yesterday @ 00:00' => mktime(0, 0, 0, 12, 31, 2009),
			'Yesterday @ 03:15' => mktime(3, 15, 0, 12, 31, 2009),
			'Yesterday @ 23:00' => mktime(23, 00, 0, 12, 31, 2009),
		);
		foreach($tests as $expected => $test){
			$this->assertEquals($expected, date::fromNow($test, $this->now));
		}
	}

	public function testNow(){
		$tests = array(
			'Now' => $this->now + (60 * 30),
			'Now' => $this->now + (60 * 15),
			'Now' => $this->now,
			'Now' => $this->now + (60 * -15),
			'Now' => $this->now + (60 * -30),
		);
		foreach($tests as $expected => $test){
			$this->assertEquals($expected, date::fromNow($test, $this->now));
		}
		$this->assertEquals('Now', date::fromNow(time()));
	}

	public function testFromNowToday() {
		$tests = array(
			'Today @ 03:15'=>mktime(3, 15, 0, 1, 1, 2010),
			'Today @ 23:59'=>mktime(23, 59, 0, 1, 1, 2010),
			'Today @ 20:00'=>mktime(20, 00, 0, 1, 1, 2010),
		);
		foreach($tests as $expected => $test){
			$this->assertEquals($expected, date::fromNow($test, $this->now));
		}
	}

	public function testFromNowTomorrow() {
		$tests = array(
			'Tomorrow @ 00:00' => mktime(0, 0, 0, 1, 2, 2010),
			'Tomorrow @ 03:15' => mktime(3, 15, 0, 1, 2, 2010),
			'Tomorrow @ 23:59' => mktime(23, 59, 0, 1, 2, 2010),
		);
		//mktime($hour, $minute, $second, $month, $day, $year)
		foreach($tests as $expected => $test){
			$this->assertEquals($expected, date::fromNow($test, $this->now));
		}
	}

	public function testThisWeek(){
		$tests = array(
			'Tomorrow @ 00:00' => mktime(0, 0, 0, 1, 2, 2010),
			'Sun 3 @ 00:00' => mktime(0, 0, 0, 1, 3, 2010),
			'Mon 4 @ 00:00' => mktime(0, 0, 0, 1, 4, 2010),
			'Tue 5 @ 00:00' => mktime(0, 0, 0, 1, 5, 2010),
			'Wed 6 @ 00:00' => mktime(0, 0, 0, 1, 6, 2010),
			'Thu 7 @ 00:00' => mktime(0, 0, 0, 1, 7, 2010),
		);
		//mktime($hour, $minute, $second, $month, $day, $year)
		foreach($tests as $expected => $test){
			$this->assertEquals($expected, date::fromNow($test, $this->now));
		}
	}

	public function testRandomDays(){
		$tests = array(
			'Jan 20 @ 00:00' => mktime(0, 0, 0, 1, 20, 2010),
			'Feb 2 @ 03:15' => mktime(3, 15, 0, 2, 2, 2010),
			'Mar 2 @ 23:59' => mktime(23, 59, 0, 3, 2, 2010),
		);
		//mktime($hour, $minute, $second, $month, $day, $year)
		foreach($tests as $expected => $test){
			$this->assertEquals($expected, date::fromNow($test, $this->now));
		}
	}

	public function testCountDays(){
		$tests = array(
			array(31, mktime(0, 0, 0, 1, 20, 2010), mktime(0, 0, 0, 2, 20, 2010)),
			array(1, mktime(0, 0, 0, 1, 20, 2010), mktime(0, 0, 0, 1, 21, 2010)),
			array(3705, mktime(0, 0, 0, 0, 0, 0), mktime(0, 0, 0, 1, 21, 2010)),
			array(1, mktime(0, 0, 0, 12, 31, 2009), mktime(0, 0, 0, 1, 1, 2010)),
			array(-1, mktime(0, 0, 0, 1, 1, 2010), mktime(0, 0, 0, 12, 31, 2009)),
			array(0, mktime(0, 0, 0, 1, 1, 2010), mktime(0, 0, 0, 1, 1, 2010)),
			array(24855, 0, 2147483647), // Value of PHP_INT_MAX PHP 5.3
			
		);
		foreach($tests as $test){
			list($expected, $start, $finish) = array_values($test);
			$this->assertEquals($expected, date::countDays($start, $finish));
		}
	}

}