Regardless which productivity system or method you prefer, Zenkit is an all-in-one webapp that can help you manage your big projects and activities using the system that works for you. It's free (for now, it's in beta), but it looks good -- minimal and distraction-free, but powerful under the hood.
At first blush, Zenkit looks downright bare (although there's a super helpful tutorial video to help you get started,) but once you start creating projects that you need to manage, it really opens up. As you begin to add to-dos and break your project down into actionable steps, you can assign specific due dates to each of your items. You can also manage your whole list of to-dos in either a simple list form, view them all in a table that's organised by what needs to be done when, see them all on a calendar you and everyone else you're working with can interact with or arrange them into tiles in a Kanban-style flow that lets you see what's on deck, what's coming up and what's completed.
If you have a "team" you have to manage you can add them, but for more practical, individual purposes, if you have anyone you work with on a project, whether it's neighbours on a community garden or family members planning a reunion, they can collaborate with you on Zenkit projects. If you prefer to manage your own to-dos, that's fine too.
Hit the link below to give it a try. I found it especially promising, and refreshing -- while there are more than enough simple to-do apps, it's nice to see something new that isn't just good at managing to-dos, but helpful to organise whole projects.