Calendar tools are digital or physical systems that help individuals and organizations manage their time effectively. They allow users to schedule events, set reminders, and track important dates. Common examples include online applications like Google Calendar and Microsoft Outlook, as well as traditional paper planners. These tools often come with features such as sharing capabilities, color-coding, and integration with other applications. They can be accessed on various devices, including smartphones, tablets, and computers, making it easy to stay organized and informed about upcoming commitments and deadlines.