Easy To Do Calendar is a free iPhone app designed by HyunSu Park for efficient task management. The app offers a simple yet effective way to track your to-dos with its unique circle-filled color system. By clicking on the circles, users can easily mark tasks as complete. Additionally, users can view the number of to-dos scheduled for the week at a glance in the top right corner.

The app provides features such as task completion tracking, iCloud syncing between iPad and iPhone, a widget, a variety of theme colors, customizable first day of the week settings, dark mode, font size adjustments, Korean language support, and the ability to attach pictures to tasks.