The term "ano" refers to a year in the context of time measurement. A year is defined as the period it takes for the Earth to complete one full orbit around the Sun, which is approximately 365.25 days. This period is divided into 12 months, each varying in length, with February being the shortest. In the Gregorian calendar, which is the most widely used calendar system today, years are numbered sequentially. The year 1 AD marks the beginning of the Common Era, while years before that are denoted as BC (Before Christ). Leap years, occurring every four years, add an extra day to February to account for the additional 0.25 days.