The Old Chinese Almanac, also known as 'Tong Shu' or the 'Selection of Auspicious Days,' is far more than a simple calendar. It is a profound discipline of traditional Chinese culture that integrates astronomy, calendar systems, philosophy, and folklore. As a classic of life spanning millennia, it represents the wisdom of the ancients in exploring the relationship between heaven and humanity, seeking harmony and order. Its core system exquisitely combines the lunar calendar, the 24 solar terms, the Heavenly Stems and Earthly Branches, and the Yin-Yang and Five Elements with the specific decisions of daily life. By deducing what is 'auspicious' (Yi) or 'inauspicious' (Ji) for each day, it provides a reference for important life events—such as farming, rituals, weddings, construction, and travel—based on natural rhythms. Behind this lies the ancient philosophy of 'following the mandate of heaven,' aiming to guide people in capturing the optimal intersection of 'timing, environment, and human harmony' to settle the mind and plan life. In modern society, consulting the almanac has transcended its role as a mere decision-making tool to become a ritualistic cultural practice. It allows us to reconnect with ancient temporal wisdom amidst a fast-paced modern life, gaining spiritual tranquility and cultural identity from tradition. Whether as a vessel for cultural research, a fun guide for daily life, or a spiritual anchor for major ceremonies, the almanac continues to provide modern people with a sense of composure and certainty across time. Today, this ancient wisdom is integrating into contemporary life in new forms (such as digital apps and creative products), continuing to serve as the 'time map' and 'life kit' of Chinese civilization.