Sort users by registration date, and then allow code to appear on certain dates.

I have users joining up all over the year, but what I would like to do is to control the user's 'welcome page' based on the date they joined. I assume it will be used with a PHP if and else, but a little more complex.

So if a user joins after september 2013, they will be able to see part of the site (PHP if ).

Once that user's account reaches september 2014, it will no longer display parts of the site (PHP else).

But any who is brand new in september 2014 will see certain parts of the code.

i.e:

If user signs up before: 09/2013 { displays code }
If user signs up before: 09/2013 { displays code }