usa una select:
Codice PHP:
Giorno
<select name="days">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">etc...</option>
</select>
Mese
<select name="month">
<option value="01">Gennaio</option>
<option value="02">Febbraio</option>
<option value="03">etc...</option>
</select>
Anno
<select name="year">
<?php $min_year 1998$max_year 2012?>
<?php 
for($year $min_year;$year $max_year$i ++){?>
<option value="<?php echo $year ?>"><?php echo $year ?></option>
<?php ?>
</select>