A century is a period of 100 years. Although a century can mean any arbitrary period of 100 years, there are two viewpoints on the nature of standard centuries. One is based on strict construction, while the other is based on popular perspective. While the century has been commonly used in the West, other cultures and calendars have utilized differently sized groups of years in a similar manner.
A year is divided into 12 months in the modern-day Gregorian calendar. Each month has either 28, 30, or 31 days during a common year, which has 365 days. During leap years, which occur nearly every 4 years, we add an extra day, Leap Day, on 29th February, making leap years 366 days long.