Source code for: http://daveyshafik.com/archives/28101-datetime-timestamp-parsing.html

basic_interval_math.php

<?php
$interval = DateInterval::createFromDateString("1 hour");

$dateTime->add($interval);

echo $dateTime->format(DateTime::ATOM); // 2012-09-01T23:20:01+01:00
?>

change_timezone.php

<?php
$timeZone = new DateTimeZone("Europe/London");

$dateTime->setTimezone($timeZone);

echo $dateTime->format(DateTime::ATOM); // 2012-09-01T22:20:01+01:00
?>

complex_interval_math.php

<?php
$interval = DateInterval::createFromDateString("1 year 3 months 8 days 2 hours");

$dateTime->add($interval);

echo $dateTime->format(DateTime::ATOM); // 2013-12-10T01:20:01+00:00
?>

date_time_var_dump.php

object(DateTime)#1 (3) {
    ["date"]=> string(19) "2012-09-01 16:20:01"
    ["timezone_type"]=> int(1)
    ["timezone"]=> string(6) "-05:00"
}

using_fuzzydate.php

<?php
echo fuzzyDate("2011-09-16T11:38:23-05:00"); // Last Friday at 11:38am
echo fuzzyDate(date(DATE_ATOM)); // Today at 11:18am
echo fuzzyDate("2011-09-21T00:00:00-05:00"); // Tomorrow at midnight
?>