Timezone free date manipulation

More info on AC Ticket#36
http://tracker.hughessg.com/ac/public/index.php?path_info=projects%2F230%2Ftickets%2F36
v3.0.1 Null date handling

As we move ahead for Chrome support. This is the first installment. Null
/ Empty dates did not behave as expected (esp for Dashboard). So, need
to explicitly set the alternate date field when dates are emptied by
user.