[Code Help]General code help?[PHP] (12)

10 Name: #!/usr/bin/anonymous : 2014-04-25 19:32 ID:x9BsBbjb

Ok, so based on what >>2-san gave me, this is what I came up with:

$days=21*12*30;//21 because it's been 21 years since 1993
$date = date("1993-09-$days);
echo $date;
Would this be correct? Because every time I check http://www.eternal-september.org/ I'm off by 18 days.
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