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Articles About Calendar (66)

Bahá'í Leap Year

The Bahá'í leap year occurs when five extra days are added between the last two months of the calendar. Leap years usually occur every four years. more

Chinese Leap Month

Instead of adding one leap day on February 29 nearly every four years, the Chinese add a leap month every 3 years to keep their calendar in line with the Earth's rotation. more

The Doomsday Rule

Some dates fall on the same weekday every year. Use this knowledge to calculate the weekday of any given date in your head. more

The Doomsday Algorithm

Some dates fall on the same weekday every year. Use this knowledge to calculate the weekday of any date in your head. more

The Ethiopian Leap Year

A leap year occurs every 4 years in the Ethiopian calendar when one extra day is added at the end of the year. more

February 30

February 30 actually existed at least twice in the past, according to historical records. more

Friday the 13th

Friday the 13th, also known as Friday 13 or Friday the thirteenth, has been considered as a day of bad luck in various countries for many years. more

The Hindu Leap Year

The Hindu leap year has an extra month and occurs once every 3 years or 4 times in 11 years. more

The Persian Leap Year

The Iranian or Persian calendar is one of the most accurate calendar systems ever devised. Find out what makes it so precise. more

Islamic Leap Year

A leap year in the tabular version of the Islamic Hijri calendar occurs 11 times in a 30-year cycle when one day is added to the last month of the year. more

Leap Day Birthdays

When do “leaplings” celebrate their birthdays – every year or only during leap years? more

Leap Year in Other Calendars

Most western countries use the Gregorian calendar, but some use other calendars. Some calendars even add a leap month instead of a leap day. more

What Is a Leap Year?

A leap year has 366 days, as opposed to a common year, which has 365. Nearly every four years is a Leap Year, and we add a leap day, an extra day on February 29. more

Palindrome Day

A Palindrome Day happens when the day’s date can be read the same way backwards and forwards. The dates are similar to word palindromes in that they are reversible. Depending on the date format Palindrome Days can be rare. more

Is There a Perfect Calendar?

Our calendar does not accurately reflect the length of a tropical year, the time it takes Earth to complete a full orbit around the Sun. Why is that so and are there other calendars that do a better job? more

Special Calendar Dates

Learn more about numerically unique calendar dates such as sequential dates, same number dates, and palindrome (reversible) dates more

The 823-Year Myth

5 Fridays, 5 Saturdays, and 5 Sundays in the same month happens only every 823 years? This popular urban myth is precisely that: a myth. more

The Chinese Calendar

The Chinese calendar is one of the oldest calendars in modern society. It is a lunisolar calendar. more

The Ethiopian Calendar

The Ethiopian calendar is quite similar to the Julian calendar, which was the predecessor to the Gregorian calendar most countries use today. more

The Julian Calendar

The Julian calendar reformed the ancient Roman calendar and consists of three cycles of 365-day years followed by a 366-day leap year. Introduced by and named after Julius Caesar in 45 BCE. more

What Is June Solstice?

The June solstice is the longest day of the year in the Northern Hemisphere & the shortest day in the Southern Hemisphere. more

End of the world December 21, 2012?

The Mayan calendar ended one of its great cycles in December 2012, which has fueled countless predictions about the end of the world on December 21, 2012 at 11:11(UTC). more

The Mayan Calendar

The Maya calendar consists of a system of three interlacing calendars and almanacs which was used by several cultures in Central America, most famously the Maya civilization. more

The Revised Julian Calendar

The Revised Julian calendar is one of the most accurate calendar systems ever developed. How does it work, and why don't we use it? more

The Roman Calendar

The ancient Roman calendar, or “pre-Julian” calendar, is believed to have been a lunar calendar. more

A Year Is Never 365 Days

The definition of a tropical year is the time it takes the Earth to complete a full orbit around the Sun. It is approximately 365.242189 days long. more

Why Are There 7 Days in a Week?

It's Monday, you have to wait 5 days till the weekend. Why does a week have 7 days, and why in that order? Thank the Moon and an ancient people in today's Iraq. more

Friday – fifth day of the week

Friday is the fifth day of the week, between Thursday and Saturday, and the last day of the working week in most western countries that follow ISO 8601. Friday is named after the Norse fertility goddess Frigg. more

The Seven-Day Week

The 7-day week is the international standard that is used by the majority of the world. There are 52 or 53 weeks in a year, but countries vary on how they count the weeks. more

Wednesday – 3rd Day of the Week

Wednesday is officially the 3rd day of the week and comes between Tuesday and Thursday. It is considered the 4th day of the week in some countries. more

What Is a Black Moon?

It can be the 3rd New Moon in a season of 4 New Moons or the 2nd New Moon in the same month or even no New Moon at all. more

First Quarter Moon

The First Quarter Moon is a primary Moon phase when we can see exactly half of the Moon's surface illuminated. If it is the left or right half, depends on where you are on Earth. more

The Full Moon

The Full Moon is the moment the entire face of the Moon is illuminated by the Sun's rays. It is the 3rd primary phase. Each Full Moon has a name, except the Blue Moon. more

The Lunar Month

A lunar month is the time it takes the Moon to pass through all of the Moon phases, usually measured from a New Moon the next New Moon. more

The New Moon

In modern astronomy, the New Moon is when the Sun and Moon are aligned, with the Sun and Earth on opposite sides of the Moon. The New Moon also has important cultural and religious significance worldwide. more

Third Quarter Moon

The Third or Last Quarter Moon is when the opposite half of the Moon is illuminated compared to the First Quarter. more

Waning Crescent Moon

During the Waning Crescent Moon phase, the illuminated part of the Moon decreases from a semicircle at Third Quarter until it disappears from view entirely at New Moon. more

The Month of April

April is the fourth month of the year in the Gregorian calendar, and is named after the Greek goddess Aphrodite. more

The Month of August

August is the eighth month of the year in the Gregorian calendar and is named after Augustus Caesar. more

The Month of February

February is the second month of the year in the Gregorian calendar. It is the shortest month with only 28 days in common years and 29 days in leap years. more

The Month of May

May is the fifth month of the year in the Gregorian calendar and named after the Greek godess Maia. more

Month of September

September is the ninth month of the year in the Gregorian calendar, but the name means 'seventh', as it was the seventh month in the ancient Roman Calendar. more

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