Date Difference Calculator
Calculate the difference between two dates
Select Dates
Date Difference
Understanding the Gregorian Calendar
The Modern Calendar System
The Gregorian calendar is the most widely used calendar system in the world today. A standard year contains 365 days, with an additional leap day added to February during leap years. Most months have either 30 or 31 days, with February being the exception at 28 days (29 in leap years).
Historical Evolution
The Gregorian calendar evolved from the Julian calendar, which itself was a modification of the ancient Roman calendar. The original Roman calendar was based on lunar cycles, but this caused seasonal misalignment over time. Julius Caesar reformed the calendar in 46 BC, introducing the concept of leap years to better align with the solar year.
The Gregorian Reform
By 1582, the Julian calendar had drifted 10 days from the solar year. Pope Gregory XIII implemented the Gregorian calendar, skipping 10 days (October 4 became October 15) and refining leap year rules. Century years are only leap years if divisible by 400, reducing calendar drift to just 1 day every 3,030 years.
US Federal Holidays Reference
Understanding Federal Holidays
Federal holidays in the United States are days recognized by the federal government when non-essential federal offices are closed and federal employees receive paid leave. Private sector observance varies by company policy. Some holidays have fixed dates, while others follow floating patterns based on specific weekdays.
2025 Federal Holidays
2026 Federal Holidays
Holiday Types
- Fixed Holidays: Always fall on the same date (e.g., New Year's Day, Christmas)
- Floating Holidays: Based on specific weekdays (e.g., MLK Day - 3rd Monday in January)
- Private Sector: Company policies may vary for federal holiday observance