The date not convert to strtotime format in php

The date not convert to strtotime format

start date= 2016-04-26 10:53:10 
end date= 2050-04-29 01:00:00
$db_start_date=strtotime($future_product_result['startdate']);
$db_end_date=strtotime($future_product_result['enddate']);

The start date convert to strtotime format = 1461648190. But the enddate not convert.