Description:
------------
No matter what I do, strtotime can't seem to handle dates prior to 1970. The answer returned is always -1. 

The manual doesn't indicate this fact. 

Reproduce code:
---------------
echo phpversion();
echo "\n------------------\n";

$time1="1/1/1970";
$time2="31-dec-1969";
$time3="31-dec-1949";

echo strtotime($time1);
echo "\n";
echo strtotime($time2);
echo "\n";
echo strtotime($time3);
echo "\n";

Expected result:
----------------
4.3.2
-----------------
28800
-{some integer other than 1} 
-{some bigger integer other than 1} 

Actual result:
--------------
4.3.2
------------------
28800
-1
-1