world clock javascript

javascript supporting multiple clocks but not showing the correct GMT time:

<table border="0" width="200" cellspacing="0" cellpadding="3"> <form name="where"> <tr> <td width="100%"> <select name="city" size="1" onchange="updateclock(this);"> <option value="" selected>Local time</option> <option value="0">London GMT</option> <option value="1">Rome</option> <option value="7">Bangkok</option> <option value="8">Hong Kong</option> <option value="9">Tokyo</option> <option value="10">Sydney</option> <option value="12">Fiji</option> <option value="-10">Hawaii</option> <option value="-8">San Francisco</option> <option value="-5">New York</option> <option value="-3">Buenos Aires</option> </select>