conditional formatting regarding dates question

I am new to formatting within Excel, and trying to make a spreadsheet regarding the expiration of dates.

Here is my problem:

I am creating a spreadsheet with multiple future dates in which a probation program runs out for many young individuals. Right now I am only using a physical paper organization and i can't possibly keep track of this without using excel. In column A I have the dates in with the probation program is supposed to be completed, and in column B I have the names of the individuals, pretty simple so far. I would like to have the excel spreadsheet automatically update and fill in with different colors when the probationary period ends in 3 months, 30 days, and a week based off of the current date. How do I get started with this formatting??