How do you build a membership function, with subscription and trial function

I want to make a mebership system, where you can have a 30 day free trial, and then sign up for monthly or yearly subscription.

My thought was that if I did not have the need for a free trial, I could make a timestamp check from the date the user registred and signed up for either a month or a year, and then hide the membership functions, when the 365 days is over.

But how would I have both the subscripment period, AND a way to make a 30 day free trial.

How can I build both control functions ?

Can anybody get me in the right direction !!