In 2016, UNESCO inscribed the Chinese solar terms on the Representative List of the Intangible Cultural Heritage of Humanity — "knowledge in China of time and practices developed through observation of the sun's annual motion." This is the calendar behind every BaZi chart.
Dates shown use the local timezone of the visitor and may shift by one day depending on where you are.
Most Chinese lunar months begin with the new moon, which is why Chinese New Year "moves" each year. The solar terms solve the opposite problem: they anchor the calendar to the sun, each term marking a precise point in the sun's journey across the year.
Because of this, the boundaries of the BaZi year and month pillars are always fixed to solar events — Start of Spring begins the new year, and each of the twelve "major" terms (节) begins a new month pillar. A BaZi chart is, in this sense, a precise astronomical record of a birth time.
Read more: The 24 Solar Terms: A UNESCO-Listed System of Time