Time zones are set at the individual account level. You can define your time zone by clicking on your username on the top right corner of your screen when you’re on your dashboard. That will take you to the account settings tab. From there, you can see and set your local time zone!
November NaNoWriMo, April Camp NaNoWriMo and July Camp NaNoWriMo all end at 11:59pm in your local time zone on the last day of the month in which they take place. Therefore, a writer in Australia may have NaNoWriMo end at 11:59pm their local time while, at the very same hour, a writer in California will still have 19 hours of NaNoWriMo left. However, NaNoWriMo started earlier for the writer in Australia than it did for the writer in California. All writers have the same amount of time to complete the challenge.