If you were to work your formula on a traditional working year, then to achieve 12 month goals, set your priorities on having 7 months to achieve them. Consider that in theory there are 110 weekend days, 10 public holidays, 10 sick leave days and 20 annual holiday days.
That eliminates 150 days from your annual calendar and leaves you 215 days or 7 months to action your goals.
This formula also helps you work out your hourly rate and the available days you have to work on your business.