A more thorough explanation:

Major annus (may-jər anəs) is a Latin term that means "the greater year." It refers to a leap year that has 366 days instead of the usual 365 days.

For example, the year 2020 was a major annus because it was a leap year with 366 days. The extra day, February 29th, is added to keep the calendar year synchronized with the astronomical year.

Another example of a major annus is the year 2024, which will also be a leap year with 366 days.

These examples illustrate the definition of major annus because they show how a leap year, with an extra day added, is considered a major annus or "greater year" compared to a regular year with 365 days.