Calendars and History
The modern calendar is a stack of compromises between the solar year, the lunar month and a good deal of Roman politics. These pieces trace how each irregularity got there — and why the leap-year rule needs an exception to its exception.
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20 articles
- How Many Weeks Are in a Leap Year?A leap year contains 52 weeks and 2 days. Learn how those extra days affect weekdays, ISO week numbers, payroll, and scheduling.7 min read
- What Is a Julian Year? Julian Year vs Calendar YearA Julian year is exactly 365.25 days for scientific calculations. Learn how it differs from Julian calendar and Gregorian calendar years.8 min read
- Why Does a Year Have 365 Days?The fascinating astronomy and history behind our 365-day calendar year.5 min read
- The History and Rules of Leap YearsWhy we add an extra day every four years, and the exceptions to the rule.4 min read
- A Brief History of CalendarsFrom lunar calendars to the Gregorian system — humanity's quest to track time.8 min read
- Why Does a Week Have Seven Days?The ancient Babylonian and astronomical roots of our seven-day week.5 min read
- How Atomic Clocks Keep Perfect TimeThe science behind the most accurate timekeeping devices ever built.6 min read
- What Are Leap Seconds?Occasionally we add a single second to the clock. Here's why — and why it may be abolished.5 min read
- The Chinese Zodiac: A Complete GuideThe twelve animals, the sixty-year cycle, and how your birth year shapes your sign.7 min read
- The Twelve Western Zodiac Signs ExplainedHow the constellations along the ecliptic became the basis for astrology.6 min read
- Birthstones by Month: The Complete ListDiscover the traditional and modern gemstone associated with every birth month.5 min read
- From Sundials to Smartwatches: A History of ClocksThe 5,000-year journey of humanity's quest to measure the passing of time.8 min read
- What Happened in October 1582? Why 10 Days DisappearedHow ten days vanished from October 1582, and why countries adopted the Gregorian calendar centuries apart.6 min read
- Why Is Friday the 13th Considered Unlucky?The surprising history behind one of the Western world's most enduring superstitions.5 min read
- Does Time Really Flow at the Same Speed?Einstein showed that time is relative — moving clocks and gravity actually change time itself.6 min read
- Lunar vs Solar Calendars: Key DifferencesWhy some calendars follow the moon, some the sun, and some try to track both.6 min read
- Julian Date vs Day of Year: What Is the Difference?Julian date, Julian day number, ordinal date, and day of year are often confused. Learn what each term means and when to use it.6 min read
- Why Does February Have 28 Days?February is shorter because of Roman calendar history, not astronomy alone. Learn how leap years and later calendar reforms shaped the month.6 min read
- Julian vs Gregorian Calendar: The Difference ExplainedCompare the Julian and Gregorian calendars, their leap-year rules, and why different historical dates can appear ten days apart.7 min read
- Calendar Week vs Workweek: What Is the Difference?Compare ordinary calendar weeks, ISO week numbers, employer-defined workweeks, and payroll periods using clear examples.7 min read