Date calculation based on month, week, day selection

Need logic

I have a scenario like this.
I select month(one radio button), week or weeks(6 check boxes) in seperate section and days in weeks(7 check boxes) in anothe section. Finally I need to calculate exact dates that were selected on these three different sections. Can anybody guide me the logic

study the calendar class and you will find the methods that allows you to calculate a date based on weeks and so on.