What is the duration of a calendar year?

The correct answer is defined by the conventional structure of a calendar year, which begins on January 1st and concludes on December 31st. This definition aligns with the Gregorian calendar, which is the most widely used calendar system today. It encompasses a full cycle of 12 months, starting in January and ending in December, totaling 365 days in a common year and 366 days in a leap year.

The other options represent fiscal years or alternative time periods that do not constitute a standard calendar year. For example, they specify various start and end dates that might be used for financial reporting or seasonal planning but fall outside the universally recognized definition of a calendar year. Understanding this conventional structure is essential for clarity in scheduling, record-keeping, and various administrative functions.