Функция TimeAgo, возвращающая отрицательные секунды

У меня есть функция, которая возвращает, как давно было опубликовано время, но, похоже, с этим возникла небольшая проблема. В первый раз $ timeAgo1 работает просто отлично, но во второй раз $ timeAgo2, похоже, возвращает отрицательные секунды. Как это происходит?

<?php

//*****************************************************START OF FUNCTION
function timeAgo($time_ago) {

$time_ago = strtotime($time_ago);
$cur_time = time();
$time_elapsed = $cur_time - $time_ago;
$seconds = $time_elapsed ;
$minutes = round($time_elapsed / 60 );
$hours = round($time_elapsed / 3600);
$days = round($time_elapsed / 86400 );
$weeks = round($time_elapsed / 604800);
$months = round($time_elapsed / 2600640 );
$years = round($time_elapsed / 31207680 );

echo $seconds."<br>";
if ($seconds <= 60) {
return "just now";
} //end of if ($seconds <= 60)

else if ($minutes <=60) {
if ($minutes == 1) {
return "one minute ago";
} //end of else if ($minutes <=60)
else {
return "$minutes minutes ago";
} //end of else not ($minutes == 1)
} //end of else if ($minutes <= 60)else if ($hours <= 24) {
if ($hours == 1) {
return "an hour ago";
} //end of if ($hours == 1)
else {
return "$hours hours ago";
} //end of else not ($hours == 1)
} //end of else if ($hours <= 24)else if ($days <= 7) {
if ($days == 1) {
return "yesterday";
} //end of else if ($days <= 7)
else {
return "$days days ago";
} //end of else not ($days == 1)
} //end of else if ($days <= 7)

else if ($weeks <= 4.3) {
if ($weeks == 1) {
return "a week ago";
} //end of if ($weeks == 1)
else {
return "$weeks weeks ago";
} //end of else not ($weeks == 1)
} //end of else if ($weeks <= 4.3)else if ($months <= 12) {
if ($months == 1) {
return "a month ago";
} //end of if ($months == 1)
else {
return "$months months ago";
} //end of else not ($months == 1)
} //end of else if ($months <= 12)

else {
if ($years == 1) {
return "one year ago";
} //end of if ($years == 1)
else {
return "$years years ago";
} //end of else not ($years == 1)
} //end of last else

} //end of function timeAgo($time_ago)
//*****************************************************END OF FUNCTION

$date1 = "2016-02-10";
$time1 = "22:41:58";
$date2 = "2016-02-12";
$time2 = "15:25:57";

$timeAgo1 = timeAgo($date1.$time1);
$timeAgo2 = timeAgo($date2.$time2);

echo $timeAgo1."<br>".$timeAgo2;

?>