Problem creating Date object from string created by Calendar

I have Calendar whose dataprovider is a global variable. When I try to create a new Date object using the updated dataprovider variable, the function returns ‘Invalid Date’.

// (user selects Fri Jun 23 11:12:27 in Calendar field)

application.output('date string: ' + globals.client_date);
application.output('date: ' + new Date(globals.client_date);

returns

date string: Fri Jun 23 11:12:27 BST 2006
date: Invalid Date

Does Date not like BST dates?