How to find first and last day of last month?.

Hello,
I am using Crystal Report XI.
Reports will be generated on first of every month for previous month. I want to find start and end date of previous month dynamic.
For august, Start date is July 1st and End date July 31st.
For September, start date is Aug 1st and Aug 31st.
How can i get first of previous month as start date and last day of the previous month as end date?.
Same kind of thing I want to do for future report ..find next month start date and end date.
Thanks