While there are some things based on time intervals, many of the maintenance items on modern cars are based on the computer assessment, or condition based services as BMW calls it. When the car was delivered, I think it also included a small pamphlet that laid out the required maintenance. I haven't looked for a long time as it has been under warranty, and the dealer took care of things as needed. That pamphlet is titled: Service and Warranty Information Booklet. If you don't have it, you can probably get one from the dealer.
2011 535i x-drive GT, 2014 i3 BEV