Common year starting on Friday facts for kids

A common year starting on a Friday is a special type of calendar year. It means that January 1st of that year falls on a Friday. A common year is a year with 365 days, which is different from a leap year that has 366 days. In the Gregorian calendar, some examples of common years starting on a Friday include 1971, 1982, 1993, 1999, 2010, and 2027. The year 2021 was also a common year that started on a Friday. In the Julian calendar, years like 2011 and 2022 are examples.

What is a Common Year?

A common year is simply a year that does not have an extra day. Most years are common years. The extra day in a leap year (February 29th) helps to keep our calendar in sync with the Earth's orbit around the Sun. Without leap years, our calendar would slowly drift out of alignment with the seasons.

Different Calendars

The world uses different ways to keep track of time. The two main calendars mentioned here are the Gregorian and Julian calendars.

The Gregorian Calendar

The Gregorian calendar is the most widely used calendar today. It was introduced in 1582 by Pope Gregory XIII. It is a solar calendar, meaning it is based on the Earth's movement around the Sun. This calendar has a rule for leap years: a year is a leap year if it is divisible by 4, unless it is divisible by 100 but not by 400. This is why the year 2100 will be a common year, even though it's divisible by 4, because it's also divisible by 100 but not by 400.

The Julian Calendar

The Julian calendar was introduced by Julius Caesar in 45 BC. It was used before the Gregorian calendar. In the Julian calendar, a leap year occurs every four years without exception. This rule made the Julian calendar slightly inaccurate over long periods, which is why the Gregorian calendar was created to fix this.

How Years Repeat

Calendars repeat in cycles. For example, a common year starting on a Friday will have the same dates fall on the same days of the week as other common years starting on a Friday. This is why you can see patterns in when these types of years occur.

Doomsday Rule (Simplified)

There's a fun trick called the "Doomsday rule" that helps you figure out the day of the week for any date. For a common year starting on a Friday, the "Doomsday" (a specific day of the week that certain dates always fall on) is a Sunday. This is a bit unique for this type of year because for most other year types, the "Doomsday" aligns differently with the ISO week date system.

See also

In Spanish: Anexo:Año común comenzado en viernes para niños