FYI, NetSuite have filled a defect on that. format.parse is indeed not working correctly with time zones and with retrieving the date time in the current user's time zone

I have also struggled with time zones in NetSuite. Depending on what your date string is you might consider adding the ISO timezone onto that string to standardize the timezone. i.e.

new Date(date + 'T08:00:00.000Z')

NetSuite just notified me that this defect was defined as U6 - meaning, not currently planned for fix. How can it be? THey have a defect in one of the basic, most used API and they are cool with that...