Get relative time in WordPress

get_the_relative_time.php

<?php
// This function will return "now", "3 seconds ago", "1 month ago" etc ...
function get_the_relative_time($time = null)
{
    if(is_null($time)) $time = get_the_time("U");
    
    $time_diff = date("U") - $time; // difference in second
    
    $second = 1;
    $minute = 60;
    $hour = 60*60;
    $day = 60*60*24;
    $week = 60*60*24*7;
    $month = 60*60*24*7*30;
    $year = 60*60*24*7*30*365;
    
    if ($time_diff <= 120) { 
        $output = "now";
    } elseif ($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{ $output = " more than a decade ago"; }
    
    if ($output <> "now") {
    	$output = (substr($output,0,2)<>"1 ") ? $output."s" : $output;
    	$output .= " ago";
    }
    
    return $output;
}