九星気学カレンダー is an Android app developed by アイスリーシステム株式会社. It falls under the category of Utilities & Tools and is available for free. This app displays the nine stars, ten stems, twelve branches, seasonal divisions, and the "doyou" (periods of extreme heat) in a calendar format. The app is compatible with the years 2001 to 2030, and users can also check the day board, month board, and year board for the selected date.

For those practicing astrology, this app provides a convenient way to access and reference these astrological elements. The app allows users to set their birth date through the menu button at the bottom of the calendar display or the three white dot buttons at the bottom of the screen.

Please note that the calculation of the monthly destiny star in this app follows the rule of "when the year and month overlap, the month shifts to the pre-natal opposite." While this may differ from other schools of astrology, the app displays the monthly destiny star as the pre-natal opposite of the main destiny star.