The article "Looking at the Lake Pavilion Snow" was written after the demise of the Ming Dynasty, but it used the calendar years of the Ming Dynasty. What's the point?

First of all, the event in this paper took place in the fifth year of Chongzhen, that is, 1632. The Ming dynasty did not perish, but the author recalled the days after it. This paper expresses the author's deep yearning for his old country and his thoughts of seclusion. The author devotes himself to the scenery, and is not exposed to the secular and chaotic outside world; But as a cultural element loyal to the Ming Dynasty, he could not help feeling deeply when he saw the change of dynasties.