On the understanding that a time picker is very similar to a date
picker, I did a few tinkerings and found..
<http://www.google.com/search?q="source+code"+"time+picker"+java+free>
returns just gets 781 hits, whereas ..
<http://www.google.com/search?q="source+code"+"date+picker"+java+free>
got 6,630 hits.

Have a scan through some from the second lot and see
if you have better luck.

HTH

Instead of implementing your own calendar, why not use free QuickTable
java component (<a
href='http://quicktable.org>http://quicktable.org</a>) which is an
implementation on top of JTable , but hides all the complexities and
allows to use the JTable methods.

In quicktable once you assign the column type as date, it will
automatically show the calendar widget once user tries to edit the
cell.

You can have a look at the calendar widget used by quicktable in the
following page
http://quicktable.org/screenshots.htm

Liz.