It's easy to add items to your calendar with TickTick, as well as add dates or reminders to your tasks so you never forget an important item again. Once you've completed a task, just check it off your list.
On top of that, you can personalize the appearance of TickTick from its options menu. It has a blue theme by default, but there are many other colors to choose from as well as the option of adding a lock pattern.
With an easy-to-use, elegant interface and loads of customization options, TickTick is a great Mac app. Check it out and keep track of all your pending tasks.