"Orthodox calendar" is a free application that includes a complete calendar of holidays and saints of the Orthodox Church for the period from 2020 to 2023. inclusive. The application does not require an internet connection. List of main functions: - Calendar of Orthodox holidays, switching the mode "Day" or "Month"; - Prayer book; - Bible. Synodal translation; - Lives of saints and description of holidays; - Evangelical and Apostolic readings; - Thoughts of Theophan the Recluse; - Sayings of the Optina elders; - Troparia and kontakia of the day; - View the date of Easter; - View twelfth and great holidays; - View days of special commemoration of the departed; - View posts and weeks; - Widgets (the application must be in the smartphone's memory, this is an Android limitation). You can view and download the application source code at https://github.com/AlexandrKozlovskiy/OrthodoxCalendar