The date picker of 04/03/16 when checked in ACF is selecting 4 March 2016 as expected, but output from the code above shows it as 3 April 2016.
I’ve spend a long time trying to work out where I might be going wrong here but have not found it. If I set a date like 17/09/16 (September 17) the output is 01/01/1970 so the code is obviously seeing it as 9th of *17th month* and recognising it as a dud date.
The strtotime() function will assume that you use the American formatting when you use ‘/’ as the date separator. Kindly use or replace it to ‘-‘ instead to make it thinks that you use the European formatting. This page should give you more idea about it: http://www.php.net/manual/en/function.strtotime.php#99149.