How many days between two dates?

Calculate days, weeks, and months between any dates

Defaults to today

Select your target date

About Leap Years

This calculator automatically handles leap years. A leap year occurs every 4 years, adding February 29th to the calendar. However, century years (like 1900) are only leap years if divisible by 400—so 2000 was a leap year, but 1900 was not. This affects date calculations spanning multiple years.

Common Uses for Date Calculations

Project Planning and Deadlines

When managing projects, knowing the exact number of days between milestones helps with realistic scheduling. Whether you're planning a product launch, tracking sprint durations, or setting client deliverable dates, calculating the precise time available prevents underestimation. A common planning mistake is assuming "about two months" when the actual period might be 45 days or 75 days—this calculator removes that ambiguity.

Contract and Legal Deadlines

Legal documents often specify deadlines in days rather than calendar dates. Notice periods, appeal windows, warranty durations, and statute of limitations all rely on accurate day counting. For example, a "90-day return policy" starting January 15th ends on April 15th, not "sometime in April." Courts and contracts require precision, making exact date calculations essential for compliance.

Age and Duration Tracking

From calculating exact ages for official documents to tracking how long you've held an investment or maintained a streak, precise duration matters. Some visa applications require knowing exactly how many days you've spent in a country. Fitness apps track workout streaks in days. Employment records may need exact tenure calculations for benefits eligibility.

Event Countdowns

Planning a wedding, retirement, vacation, or any significant life event often involves counting down the days. Knowing you have exactly 127 days until your trip helps with preparation timelines—booking flights 90 days out, requesting time off 60 days ahead, or starting a fitness routine with a specific end goal in mind.

Calendar Days vs. Working Days

This calculator provides calendar days—every day including weekends and holidays. For business contexts, you may need to convert to working days (also called business days). As a general rule, multiply calendar days by 5/7 (approximately 0.71) to estimate working days, though this doesn't account for holidays.

For example, 30 calendar days typically contains about 21-22 working days, depending on how weekends fall. A calendar month might have anywhere from 20 to 23 working days based on its length and weekend alignment. February 2024 had exactly 20 working days, while March 2024 had 21.

When contracts or deadlines specify "business days," they usually mean Monday through Friday, excluding public holidays. A "10 business day" deadline could span anywhere from 12 to 16 calendar days depending on weekends and holidays. Always clarify which type of days a deadline uses to avoid confusion.

Quick Reference: On average, one month contains about 21-22 working days, one quarter contains about 63-65 working days, and one year contains approximately 260-262 working days (varies by country and holidays).

Understanding Calendar Complexity

The Gregorian calendar we use today was introduced in 1582 to correct drift in the older Julian calendar. The Julian calendar assumed a year was exactly 365.25 days, but the actual solar year is about 11 minutes shorter. Over centuries, this small difference caused the calendar to drift significantly from astronomical events like equinoxes.

The Gregorian reform introduced the century-year rule for leap years: years divisible by 100 are not leap years unless also divisible by 400. This adjustment makes the average calendar year 365.2425 days, much closer to the actual solar year of approximately 365.2422 days. The remaining tiny discrepancy amounts to about one day every 3,236 years.

Different countries adopted the Gregorian calendar at different times—Catholic countries in 1582, Britain and its colonies in 1752, Russia not until 1918, and Greece in 1923. This means historical date calculations across different regions can be complicated by which calendar was in use at the time. This calculator uses the proleptic Gregorian calendar, applying modern rules consistently to all dates.

Time zones add another layer of complexity to date calculations. A single moment in time can fall on different dates depending on location—when it's 11 PM on January 1st in New York, it's already January 2nd in London. For most practical purposes, this calculator treats dates as whole calendar days without time-of-day considerations.

Interesting Date Facts

A non-leap year has exactly 52 weeks and 1 day, which is why dates shift forward by one day of the week each year.
The longest possible gap between two leap years is 8 years—for example, from 1896 to 1904 (1900 was not a leap year).
There are exactly 146,097 days in every 400-year cycle of the Gregorian calendar, making the calendar repeat exactly.
September, April, June, and November always have 30 days. February has 28 or 29. All others have 31.
The year 2000 was a rare century leap year—the next one won't occur until 2400.

Frequently Asked Questions

How does this calculator handle leap years?
The calculator automatically accounts for leap years when calculating days. February has 29 days in leap years (every 4 years, except century years not divisible by 400).
Why do the weeks and days not add up exactly?
Weeks are calculated as complete 7-day periods. For example, 10 days equals 1 week plus 3 days. The total days shown is always exact.
Can I calculate dates in the past?
Yes, you can select any past or future date. If the "To" date is before the "From" date, results will be shown as negative values.
How are months calculated between dates?
Months are calculated based on calendar months. A full month is counted when the day of the month in the end date is equal to or greater than the start date's day.
Does this calculator include the start and end dates?
The calculator counts the days between dates, not including both endpoints. For example, January 1 to January 3 equals 2 days. If you need to include both dates, add 1 to the result.
How do I calculate working days instead of calendar days?
This calculator shows calendar days (all days including weekends). To estimate working days, multiply by 5/7 (about 71%). For precise business day calculations, you would also need to account for public holidays in your region.
Can I calculate dates across different centuries?
Yes, the calculator handles any date range. It correctly applies leap year rules including the century exception (1900 was not a leap year, but 2000 was). Calculations spanning hundreds of years are accurate.
Why might my calculation differ from another date calculator?
Differences usually stem from how endpoints are counted (inclusive vs exclusive), timezone handling, or whether the calculator uses the Julian or Gregorian calendar for historical dates. This calculator uses exclusive counting with the proleptic Gregorian calendar.