Trouble with adding date to databse

[Rony]

I have 3 listboxes on my form, one for the day, one for the month and one for the year. I make the date as follows:

$day=$POST['Day'];
$month=$POST['Month'];
$year=$_POST['Year'];
$birthdate=$year.'-'.$month.'-'.$day;

I write to the database...

$query = "INSERT INTO inschrijvingen VALUES ('','',' ... ,'$birthdate' ...... )";

mysql_query($query);

there is no error given but in de field $birthdate there is only
0000-00-00 ?
What i'm doing wrong???

By the way: sorry for my poor englisch and thanks for any help

[Roger_Ramjet]

First step, echo out the query string BEFORE you run it to see what is being submitted to the db.

[Rony]

yes, thats the clue, in my listbox month i only used words for the months, now i still use words but also a value for each month.
Now the date is writen correct to the database