Orthodox Calendar is an Android app developed by David Leselidze. It is a comprehensive app designed for Orthodox Christians, providing them with essential information about the liturgical year. The app features lives of the saints, icons, troparions, and kontakions. It also includes daily scripture readings, feasts, fast days, and days of remembrance.

One of the key features of Orthodox Calendar is that it follows the Julian Version or "Old Calendar". This makes it an ideal app for those who follow the old calendar. The app is available in both English and Russian languages. The user interface is intuitive and easy to navigate. Overall, Orthodox Calendar is a must-have app for Orthodox Christians who want to stay connected to their faith and traditions.