How to change date format in string?

I've this on my reservation form

$day_dol = ($_POST['day_dol']);
$month_dol = ($_POST['month_dol']);
$year_dol = ($_POST['year_dol']);
$day = ($_POST['day']);
$month = ($_POST['month']);
$year = ($_POST['year']);
$datum_dolaska= "$year_dol-$month_dol-$day_dol";
$datum_odlaska = "$year-$month-$day";

$dolazak = date("Y-m-d", strtotime($datum_dolaska));
$odlazak = date("Y-m-d", strtotime($datum_odlaska));

echo " $dolazak,$odlazak ";

I put b.e $datum_dolaska= "2009-August-01" and $datum_odlaska = "2009-August-03". And I want by example put on my form reservation "2009-08-01" like day of arrival and "2009-08-03" like day of leaving. But I got it "1970-01-01" both dates. What is the problem? Thank you forward on helping me!

 

i think because post variables are not passing any values to $datum_dolaska
and why u r using 2 variables in same name if u want to show different u need to change variable names..

here is what should u do:
$datum_dolaska1= "$year_dol-$month_dol-$day_dol";
$datum_odlaska2 = "$year-$month-$day";

$dolazak1 = date("Y-m-d", strtotime($datum_dolaska1));
$odlazak2 = date("Y-m-d", strtotime($datum_odlaska2));

echo " $dolazak1,$odlazak2 ";

 

They were already different variable names they just look very similar

echo out
$datum_dolaska
$datum_odlaska

make sure they are yyyy-mm-dd or yy-mm-dd

and then echo out
echo strtotime($datum_dolaska);
echo strtotime($datum_odlaska);

and you can see where it is going wrong