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.
The unit of measurement "day" is defined as 86,400 SI seconds and symbolized d. A day is usually 24 hours, plus or minus a possible leap second in Coordinated Universal Time (UTC), and occasionally plus or minus an hour in those locations that change from or to daylight saving time.