A century (From the Latin cent, one hundred) is one hundred consecutive years. Centuries are numbered ordinally (for example "The Seventh Century AD"). Start and End in the Gregorian Calendar According to the Gregorian calendar, the 1st century AD started on January 1, 1 and ended on December 31, 100. The 2nd century started at year 101, the third at 201, etc. The n-th century will start on the year 100×n - 99. A century will only include one year, the centennial year, that starts with… (More on Century)