you can find the day of the week using one of the date functions (forget which.. may be datepart() may be weekday()).
calculating whether its the first or second week of the month is fraught with difficulties, purely based on what rules you use to identify the nth week of the month.
having found what todays date is (or arguably the first of the month you can then derive whatever values you require using dateadd() to generate a date in the future or past.
depending on how complex your week/financial year is you may need to implement a working calendar which provides a method translating real world dates into the obscure and arcane calendar that only accountants want to understand.. the financial year calendar.
I'd rather be riding on the Tiger 800 or the Norton