A century common year is a common year in the

Gregorian Calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years di ...

that is divisible by 100 but not 400. Like all common years, these years do not get an extra day in February, meaning they have 365 days instead of 366. These years are the only common years that are divisible by 4. In the obsolete

Julian Calendar The Julian calendar, proposed by Roman consul Julius Caesar in 46 BC, was a reform of the Roman calendar. It took effect on , by edict. It was designed with the aid of Greek mathematics, Greek mathematicians and Ancient Greek astronomy, as ...

, all years that were divisible by 4 were leap years, meaning no century years could be common years. However, this rule adds too many leap days, resulting in the calendar drifting with respect to the seasons, which is the same thing that would happen if there were no leap years at all. So, in 1582,

Pope Gregory XIII Pope Gregory XIII ( la, Gregorius XIII; it, Gregorio XIII; 7 January 1502 – 10 April 1585), born Ugo Boncompagni, was head of the Catholic Church and ruler of the Papal States from 13 May 1572 to his death in April 1585. He is best known for ...

introduced a slightly modified version of the Julian Calendar, the

, where century years would not be leap years if they are not divisible by 400. Therefore,

1700 As of March 1 ( O.S. February 19), where then Julian calendar acknowledged a leap day and the Gregorian calendar did not, the Julian calendar fell one day further behind, bringing the difference to 11 days until February 28 ( O.S. February 17 ...

is the first century year in the

being a common year. The years

1800 As of March 1 ( O.S. February 18), when the Julian calendar acknowledged a leap day and the Gregorian calendar did not, the Julian calendar fell one day further behind, bringing the difference to 12 days until February 28 ( O.S. February 16), ...

and

1900 As of March 1 ( O.S. February 17), when the Julian calendar acknowledged a leap day and the Gregorian calendar did not, the Julian calendar fell one day further behind, bringing the difference to 13 days until February 28 ( O.S. February 15), ...

were also century common years, and so will

2100 In contemporary history, the third millennium of the anno Domini or Common Era in the Gregorian calendar is the current millennium spanning the years 2001 to 3000 (21st to 30th centuries). Ongoing futures studies seek to understand what is l ...

2200 In contemporary history, the third millennium of the anno Domini or Common Era in the Gregorian calendar is the current millennium spanning the years 2001 to 3000 (21st to 30th centuries). Ongoing futures studies seek to understand what is l ...

2300 In contemporary history, the third millennium of the anno Domini or Common Era in the Gregorian calendar is the current millennium spanning the years 2001 to 3000 (21st to 30th centuries). Ongoing futures studies seek to understand what is l ...

, 2500, 2600, 2700, 2900, and 3000. The

repeats itself every 400 years, so century common years start on a

Friday Friday is the day of the week between Thursday and Saturday. In countries that adopt the traditional "Sunday-first" convention, it is the sixth day of the week. In countries adopting the ISO-defined "Monday-first" convention, it is the fifth da ...

if the remainder obtained when dividing the year by 400 is 100,

Wednesday Wednesday is the day of the week between Tuesday and Thursday. According to international standard ISO 8601, it is the third day of the week. In countries which have Friday as their holiday, Wednesday is the fifth day of the week. In countries ...

if the remainder is 200, and

Monday Monday is the day of the week between Sunday and Tuesday. According to the International Organization for Standardization's ISO 8601 standard, it is the first day of the week and in countries that adopt the "Sunday-first" convention, it is ...

if the remainder is 300. This means that

century leap year A century leap year is a leap year in the Gregorian calendar that is evenly divisible by 400. Like all leap years, it has an extra day in February for a total of 366 days instead of 365. In the obsolete Julian calendar, all years that were divisi ...

s always begin on a

Saturday Saturday is the day of the week between Friday and Sunday. No later than the 2nd century, the Romans named Saturday ("Saturn's Day") for the planet Saturn, which controlled the first hour of that day, according to Vettius Valens. The day's ...

References

Sources

External links

An Introduction to Calendars courtesy of the United States Naval Observatory

Units of time Calendars Julian calendar {{time-stub