The discussion centers on the insertion of leap days in solar calendars, particularly when the year begins on March 1 instead of January 1. It clarifies that leap years are determined by a four-year cycle, but the timing of leap day insertion can vary based on the calendar system in use. Specifically, when the year starts in March, the leap year would be recognized differently, potentially leading to confusion about which year is considered a leap year. The leap day was often inserted one year late during the period of calendar use, depending on ecclesiastical decisions. Overall, the determination of leap years is influenced by historical practices and adjustments made by the Church.