To generate and identify the cycling date, months, years by the combination of 10 Heavenly Stems and 12  Earthly Branches. For example, 1A, 2B, 3C, 4D, 5E, 6F, 7G, 8H, 9I, 10J, 1K, 2L, 3A, 4B, .... which are substituted by Chinese characters.

The American Apparel t-shirt is the smoothest and softest t-shirt you'll ever wear. Made of fine jersey, it has a durable, vintage feel. These classic-cut shirts are known for their premium quality, as well as ability to stand up to a washing machine (will keep size and color after many washings). The shirts are 100% fine jersey cotton, except for the heather grey color (90% cotton, 10% polyester).