The Druk Zakar App provides a 12-month day-to-day astrological calendar based on the Bhutanese lunar year. Derived from the Datho (book of astrology) published by the Dratshang Lhentshog, the council for religious affairs in Bhutan, Druk Zakar shows in detail what the day is good for and not good for, such as hoisting prayer flags or starting any important work.