Calendar Converter
Julian Date Input
📅 Quick Facts
- The Gregorian calendar was introduced by Pope Gregory XIII in 1582
- 10 days were removed: Oct 4, 1582 (Julian) → Oct 15, 1582 (Gregorian)
- Different countries adopted it over 350 years!
Calendar Comparison
🌍 Adoption Timeline
The Missing Days of History
When countries switched to the Gregorian calendar, they had to "skip" days to align with the new system. Explore what happened to these "missing" days.
🤔 Common Misconceptions
- People didn't "lose" days of their lives - they just changed the numbering
- The day of the week continued normally (e.g., Thursday Oct 4 → Friday Oct 15)
- Workers still got paid for the "missing" days in most places
- Some countries took centuries to adopt the new calendar
Historical Events Date Converter
See how famous historical dates appear in both calendar systems.
Convert Your Own Historical Date
World Calendar Systems Comparison
Compare dates across different calendar systems used around the world.
📊 Calendar Statistics
Persian (Solar Hijri) - Error of 1 day in 110,000 years
Gregorian - Official in most countries
Hebrew - Over 3,700 years old
The History & Science of Calendars
📚 Why the Calendar Changed
The Julian calendar, introduced by Julius Caesar in 45 BCE, had a year of 365.25 days. However, the actual solar year is 365.2425 days. This 0.0075-day difference caused the calendar to drift by about 1 day every 128 years.
By 1582, the spring equinox had drifted 10 days from its original date, affecting the calculation of Easter. Pope Gregory XIII commissioned a reform to fix this drift.
🔬 The Mathematics Behind the Reform
Julian Calendar: Every 4th year is a leap year
Average year = 365 + 1/4 = 365.25 days
Gregorian Calendar: Leap year except centuries not divisible by 400
Average year = 365 + 1/4 - 1/100 + 1/400 = 365.2425 days
This gives an error of only 1 day in approximately 3,030 years!
🌍 The Politics of Calendar Reform
- Religious Division: Protestant countries initially rejected the "Papist" calendar
- Economic Impact: Merchants had to deal with different dating systems
- Social Confusion: "Give us back our eleven days!" riots in Britain (1752)
- Legal Issues: Contracts and birthdays had to be recalculated
- Scientific Necessity: Astronomers needed accurate dating
🎂 Famous People Affected by the Change
- George Washington: Born Feb 11, 1731 (OS) = Feb 22, 1732 (NS)
- Cervantes & Shakespeare: Died on the "same date" but 10 days apart
- Isaac Newton: Born Dec 25, 1642 (OS) = Jan 4, 1643 (NS)
- Galileo: Lived through the actual reform in Italy
⚡ Leap Year Rules Explained
A year is a leap year if:
- It is divisible by 4 AND
- If divisible by 100, it must also be divisible by 400
Examples:
- 1900: Divisible by 100 but not 400 = NOT a leap year
- 2000: Divisible by 400 = IS a leap year
- 2024: Divisible by 4, not a century = IS a leap year
🔮 Future Calendar Proposals
World Calendar: Every year identical, quarters equal
International Fixed Calendar: 13 months of 28 days
Hanke-Henry Calendar: Permanent calendar, no date changes
Despite various proposals, the Gregorian calendar's entrenchment in global systems makes change unlikely.