What does the day after the eight characters mean?

Is it based on the year of death or birthday! Heavenly stems and earthly branches pairwise collocation, Tiangan 18, Dizhi 12, ten days is ten days, that is, after Jiazi is arranged in order, the remaining garrison is Xunkong, that is, empty death! The sky pushed down from the annual column. Baidu, look at the column of the sun is empty! There should be an explanation!