Need to find the number of days between two dates? Enter your start date and end date in the calculator above. You'll get the total number of days, weeks, months, and years instantly.
This free date calculator also lets you add or subtract days from a given date. Use it for project deadlines, age calculations, milestone planning, or figuring out how many days are left until an important date.
How This Date Calculator Helps Users
Planning around dates usually means grabbing a calendar and counting squares. That works for short stretches, but it gets trickier across months with varying month lengths or a leap year.
This calculator handles the math for you. Enter two dates and get a precise breakdown of the duration between two dates in calendar days, weeks, months, and years. Or pick a particular date and add or subtract a number of days to land on a new date.
Everything runs entirely in your browser. No sign-up, no app download, no cost. It correctly handles leap years, varying month lengths, and the shift between calendar years so you can trust the results.
Key Features of the Days Calculator
- Date difference mode. Calculate the difference between two dates in total calendar days, weeks, months, and years.
- Add or subtract days mode. Start from any date and add or subtract a number of days to find a future or past date.
- Leap year support. The calculator calculates February 29 automatically for years divisible by 4 (with the century-year exception for years divisible by 400).
- Business day awareness. Understand the distinction between calendar days and business days, excluding weekends and federal holidays.
- Instant results. No page reload. Pick your dates and the answer appears immediately.
How to Calculate the Days Between Two Dates
Enter a Start Date and End Date
Select your start date in the first field. Then select your end date in the second field. The calculator finds the duration between two dates as soon as both fields are filled.
Does the start date count as day 1, or day 0? By default, the calculator uses exclusive counting. The start date is day 0 and the end date is the final counted day. For example, January 1 to January 2 equals 1 day, not 2. This matches how most people think about a span of time: "How many days until…"
If your result differs from another tool by 1 day, inclusive vs. exclusive counting is almost always the reason.
Calculate the Date Difference in Calendar Days
The primary result is the total number of days between the two dates. This counts every calendar day, including weekends, holidays, and leap days.
You'll also see a breakdown in months and years. Keep in mind that adding 1 month doesn't always equal 30 or 31 days. Months range from 28 days (February in a common year) to 31 days, so the calculator tracks actual calendar lengths rather than using a flat average.
Can I calculate the difference in weeks or months? Yes. The result displays the date difference in multiple units so you can use whichever fits your situation.
Days Between Dates vs. Business Days
Calendar days include every day on the calendar. Business days exclude weekends (Saturday and Sunday) and, depending on context, federal holidays.
When you need business days for a work deadline or legal filing, count only weekday dates. The section below on holidays explains which federal holidays are commonly excluded.
For most personal planning (countdowns, age calculations, travel), calendar days are the right number.
How to Add or Subtract Days From a Date
Use a Date to Add or Subtract a Number of Days
Switch to add/subtract mode. Enter a starting date and the number of days you want to add. The calculator returns the resulting future date.
This is useful for:
- Figuring out a due date 90 days from today
- Setting a follow-up reminder a certain number of days ahead
- Calculating warranty or return-policy expiration dates
You can also add weeks. Just multiply the number of weeks by 7 and enter that as your day count.
Subtract From a Date to Find an Earlier Date
To find an earlier date, enter your known date and subtract the number of days. The result is the past date that falls that many days before your reference point.
Example: You know a deadline is March 15, 2025, and you need to start 60 days beforehand. Subtract 60 days from March 15 to land on January 14, 2025.
This works the same across month and year boundaries. The calculator adjusts for varying month lengths and leap years automatically.
How the Calendar Handles Leap Year
Why a Leap Year Changes the Number of Days Between Two Dates
A standard year has 365 days. A leap year has 366 days because February gains an extra day (February 29).
A year is a leap year if it meets these rules:
- It is divisible by 4.
- If it is also divisible by 100, it must also be divisible by 400.
So 2024 is a leap year (divisible by 4). The year 1900 was not a leap year (divisible by 100 but not by 400). The year 2000 was a leap year (divisible by 400).
When your date range spans February of a leap year, the calculator adds that extra day. If it doesn't, your total will be off by 1 day. This calculator handles leap years correctly every time.
Gregorian Calendar vs. Julian Calendar
The calendar most of the world uses today is the Gregorian calendar, introduced in 1582. It refined the older Julian calendar by adjusting the leap year rule for century years.
Under the Julian calendar, every year divisible by 4 was a leap year, with no exception for century years. That created a small drift over centuries. The Gregorian calendar fixed this by requiring century years to also be divisible by 400.
This calculator uses the Gregorian calendar. If you're working with historical dates before 1582, be aware that the Julian calendar was in use, and date arithmetic across that boundary can shift by several days.
Some cultural and religious calendars (like the Hijri or lunar calendar) follow different rules entirely. This tool is designed for Gregorian calendar dates.
Days Between Two Dates and Holidays
Federal Holidays in the United States and Business Days
When calculating business days, you may need to exclude federal holidays in addition to weekends. The United States recognizes 11 federal holidays:
- New Year's Day (January 1)
- Martin Luther King Jr. Day (third Monday in January)
- Presidents' Day (third Monday in February)
- Memorial Day (last Monday in May)
- Juneteenth (June 19)
- Independence Day (July 4)
- Labor Day (first Monday in September)
- Columbus Day (second Monday in October)
- Veterans Day (November 11)
- Thanksgiving Day (fourth Thursday in November)
- Christmas Day (December 25)
Not every employer or industry observes all 11. Courts, government agencies, and banks typically do. Private businesses vary.
When a federal holiday falls on a weekend, the observed date usually shifts to the nearest weekday (Friday for Saturday holidays, Monday for Sunday holidays).
For precise legal or payroll deadlines, confirm which holidays apply to your situation. This calculator gives you the calendar day count. Adjust for holidays manually based on the rules that apply to you.
How to Use a Date Calculator for Two Dates at a Glance
- Pick your mode. Choose whether you want the duration between two dates or want to add or subtract days from a date.
- Enter your dates. Select the start date and end date (or a start date and number of days).
- Read the result. The calculator shows calendar days, plus a breakdown in weeks, months, and years where applicable.
- Adjust as needed. Swap dates, change the day count, or toggle between modes without reloading the page.
The result is an estimate for personal planning. For legal filings, contract deadlines, or financial calculations, verify requirements with the relevant authority. Court deadlines, for instance, may have specific rules about excluding weekends and holidays that differ from a general-purpose date calculator.