Android/iOS/OSX: If you prefer the GTD Philosophy, 2Do might be the best tool to help you organise your time. It's both a calendar and task management app, with some powerful features that make planning easy.
You can capture everything with the GTD inbox, from tasks to ideas to reminders. You can break down your larger tasks into smaller ones by nesting your lists into larger list-groups. Then, when you're looking them over to reflect, you can pinch to zoom in and out of a task to gain a better perspective and focus. There's also batch editing, keyboard shortcuts for iPad, drag and drop, sort by tags and a nearby panel so you can get alerts when there's something to be done nearby.
The primary features for all three platforms include Smart Lists, a powerful search that includes everything from date range to the ability to pull up words that sound alike in case of a typo. There's also Smart Scheduling, which keeps your task list updated when something is due, without you having to go in and manually change it. Everything can be synced with Dropbox, Toodledo and Reminders. The Mac App enables the use of hotkeys, so you can quickly navigate the app and plan your day.
2Do comes with a hefty price tag, so it's not for someone who's just getting the hang of task management. If you're a power user of the GTD productivity method, 2Do should have everything you're looking for. Hit the links below to find out more and download the app.