Since the current lunar calendar uses the fixed conjunction (the exact astronomical event when the moon is not visible) as the first day of each month, the number of days between two first days is determined by astronomical phenomena and is not fixed. Therefore, this situation may occur. In rare years, there have even been cases where four consecutive large months occurred in the lunar calendar.

　　Although the number of days in a lunar month is determined by the fixed conjunction, which can be inconvenient for people to remember, it is more in line with astronomical phenomena and is more progressive compared to the mean conjunction in terms of astronomy.