If you select Weeks, you must define how weeks aggregate, as they do not divide evenly into months, quarters and years.
To handle extra days:
Select an option:
Adding a 53rd week as needed—Adds extra weeks as needed
Ignoring them—Discards extra days. Years contain 52 weeks/364 days.
Click Next.
SeeSpecify the Number of Months in a Year.
To handle extra days: