Calendar.js: May be the Best Web-based Calendar yet
Calendar.js is a free open source web-based calendar app. It features dozens of useful features and a responsive customizable interface.
One of the best features here is it allows you to control your events by drag-and-drop, duplicate events, add translated events, and even group your events.
You can create custom events, export and import your events in different formats, schedule and repeat events, search your events and more.
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The project is released under the GPL-3.0 License.