Creating a timeline for your story doesn't need to be a literal timeline of dates. You can do a list of the events in the order they occur, and if anything is non-linear (if you have flashforwards, flashbacks, or show things happening out of order or backwards) just make a note of that. If it's a non-linear story, you can even do two separate lists, one list of things in the order they happen and one list of things in the order you tell them. Best of luck!