datetime select

Is there an easy way to limit the time portion on a datetime_select to
only every 15 minutes? ie, restrict minute selection on the form to
only: :00, :15, :30, :45 -

Also, can I set it as a 12-hour clock instead of 24-hr?

here's what I have now:

<%= datetime_select( :schedule, :coursedate, :order =>
[:month,:day,:year] ) %>

Thanks in advance for your help.

sorry, can't help you with datetime_select,
but maybe that's an interesting alternative:

http://code.google.com/p/calendardateselect/