六壬 is a mobile application developed by Windsails that is based on ancient astronomical calendar and related knowledge. It combines the principles of Taiji, Yin Yang, Wuxing, Gossip, Ganzhi, and Jiugong, making it a comprehensive tool for operations, deductions, and judgments. It is known as one of the three styles, along with Taiyi and Qimen, with Taiyi focusing on heavenly matters and Qimen on geographical aspects. The Six Squares, on the other hand, focuses on human affairs, making it the largest among the three.

The app provides various features, including the ability to input basic information such as time, gender, and birth year to generate a Six Squares chart. It displays corresponding information such as solar energy, year life, space-time, third pass, four lessons, and heaven and earth. The app also allows for customization of parameters and starting modes, and provides detailed analysis of each house. Additionally, it offers features such as age of the year, season, month, and day, as well as powerful matching queries and data backup options.

Please note that the free version of the app contains advertisements and some features may be randomly blocked. However, all the basic features are still available, making it a useful tool for those interested in ancient astrological practices.