Is 1 sec the smallest unit of time? There are milliseconds, subtle, and infinitely accurate as long as you want.
Of course, it is impossible for the ancients to have such accurate instruments. Generally speaking, they adopted an algorithm accurate to the hour.
Therefore, eight-character numerology is not 100% accurate. And the eight characters only represent a kind of innate qi. The fate of a person's life also includes many acquired opportunities and so on. In ancient times, real masters would consider your face, palm reading and horoscope at the same time and discuss your fate comprehensively. The accuracy is much higher.