Regarding the booking of RTWs...

I understand that all travel needs to be completed within 330 days (?) of the trip's commencement. If I'm planning to start a RTW in 10 months, I can't book flights using the online tool for greater than 365 days (?) from today. So... how do I do it?

Also, once ticketed, what are the penalties, etc. and implications associated with a date change? Either before or after the first leg is flown?

Thanks!