Many popular social networking sites such as Digg or Twitter don’t display dates like Published on June 25. Instead, they display Published 10 days ago.
Here’s a PHP function to convert a date into a “time ago” date.

function  timeAgo($timestamp, $granularity=2, $format='Y-m-d H:i:s'){
        $difference = time() - $timestamp;
        if($difference < 0) return '0 seconds ago';
        elseif($difference < 864000){
                $periods = array('week' => 604800,'day' => 86400,'hr' => 3600,'min' => 60,'sec' => 1);
                $output = '';
                foreach($periods as $key => $value){
                        if($difference >= $value){
                                $time = round($difference / $value);
                                $difference %= $value;
                                $output .= ($output ? ' ' : '').$time.' ';
                                $output .= (($time > 1 && $key == 'day') ? $key.'s' : $key);
                                $granularity--;
                        }
                        if($granularity == 0) break;
                }
                return ($output ? $output : '0 seconds').' ago';
        }
        else return date($format, $timestamp);
}

Usage

$time = timeAgo($dateRef);

The function takes 3 parameters:

• timestamp: Your date
• granularity: How far you go in the precision of your date. Default is 2 (1 day, 15 hours ago)
• format: Desired format for the date. Default is Y-m-d H:i:s.

Using the timeAgo() function within WordPress

Using timeAgo() in WordPress is not hard at all. Use the following code within WordPress loop to display the “time ago” date of a post:

echo timeAgo(get_the_time('U'));