Need help with RANKX within a date range

I want to numerically rank an amount within a specific date. Say my data is this.

Person	Sales	Date
Bob	10	January
Jeff	20	January
Steve	30	January
Bob	50	February
Jeff	40	February
Steve	30	February
Bob	20	March
Jeff	30	March
Steve	10	March

 I want to be able to see their ranks with a month and also for the entire year. Like this.

Person	Sales	Date	Month Rank	Year Rank
Bob	10	January	3	2
Jeff	20	January	2	1
Steve	30	January	1	3
Bob	50	February	1	2
Jeff	40	February	2	1
Steve	30	February	3	3
Bob	20	March	2	2
Jeff	30	March	1	1
Steve	10	March	3	3

I'm having difficulty getting the ranks within the months. It ranks each record individually so in this case it shows ranks 1-9. 

Thanks!