There are four types of weeks to concern yourself with:
Week of Year (1-53). Hierarchy: Year > Week
You should decide whether you want Week 1 to begin on Jan 1, or follow the ISO standard
Week of Month (1-5). Hierarchy: Year [> Quarter] > Month > Week
You should decide whether you want Week 1 to begin on the first day of the month, or the first Sunday/Monday of the month.
Week of Fiscal Year (1-53). Hierarchy: Fiscal Year > Week
Week of Fiscal Month (1-5). Hierarchy: Fiscal Year [> Quarter] > Month > Week