get_the_relative_time.php

<?php
// This function will return "now", "3 seconds ago", "1 month ago" etc ...
// example: echo 'posted ' . get_the_relative_time(mktime(date("H"), date("i"), date("s"), date("m")-1,   date("d"),   date("Y")));

function get_the_relative_time($time = null, $now = 20) {
    if(is_null($time)) $time = date('U');
    
    $time_diff = date("U") - $time; // difference in seconds
    
    $second = 1;
    $minute = 60;
    $hour   = 60*60;
    $day    = 60*60*24;
    $week   = 60*60*24*7;
    $month  = 60*60*24*30;
    $year   = 60*60*24*365;

    $decade = false;
    
    if ($time_diff <= $now) {
        $output = "now";
    } elseif ($time_diff > $second && $time_diff < $minute) {
        $output = round($time_diff/$second)." second";
    } elseif ($time_diff >= $minute && $time_diff < $hour) {
        $output = round($time_diff/$minute)." minute";
    } elseif ($time_diff >= $hour && $time_diff < $day) {
        $output = round($time_diff/$hour)." hour";
    } elseif ($time_diff >= $day && $time_diff < $week) {
        $output = round($time_diff/$day)." day";
    } elseif ($time_diff >= $week && $time_diff < $month) {
        $output = round($time_diff/$week)." week";
    } elseif ($time_diff >= $month && $time_diff < $year) {
        $output = round($time_diff/$month)." month";
    } elseif ($time_diff >= $year && $time_diff < $year*10) {
        $output = round($time_diff/$year)." year";
    } else{ $decade = true; $output = " more than a decade ago"; }
    
    if ($output != "now" && !$decade) {
    	$output = (substr($output,0,2)<>"1 ") ? $output."s" : $output;
    	$output .= " ago";
    }
    
    return $output;
}