Date Calculator
This date calculator finds the exact number of days, weeks, months, and years between any two dates. You can also add or subtract days from a specific date to find a future or past date, with options to count only business days.
Frequently Asked Questions
How many days are between two dates?
To find days between dates, subtract the earlier date from the later date. Our calculator handles this automatically, including leap years and varying month lengths. For example, from January 1 to March 1 in a non-leap year is 59 days, but 60 days in a leap year.
How do you calculate days between two dates?
To calculate days between two dates, subtract the earlier date from the later date. Convert both dates to a common reference (such as Julian Day Number or Unix timestamp), then find the difference. For example, from January 1 to March 15 in a non-leap year: 31 days (Jan) + 28 days (Feb) + 15 days (Mar) = 74 days. Our calculator handles all the complexity of varying month lengths, leap years, and calendar rules automatically.
How do you add days to a date?
To add days to a date, start from the given date and count forward the specified number of days, accounting for varying month lengths and leap years. For example, adding 45 days to January 20 means counting through the remaining 11 days of January (to Jan 31), all 28 days of February (non-leap year), and 6 more days into March, giving you March 6. Our calculator handles this instantly for any number of days.
How many business days are in a year?
A standard year has 260 business days (52 weeks x 5 weekdays), minus public holidays. In the US, with 11 federal holidays, there are typically 249 business days per year. Leap years may add one business day if the extra day falls on a weekday.
What date is 30 days from today?
Use our Date Calculator's 'Add/Subtract Days' tab. Select today's date, enter 30 in the days field, and the calculator instantly shows the resulting date with the day of the week.
How do you calculate the difference between two dates manually?
Count the remaining days in the start month, add the full days in each intermediate month, then add the days in the final month. Or convert both dates to their day-of-year number and subtract. For dates across different years, add 365 (or 366 for leap years) for each full year.
What is a leap year and how does it affect date calculations?
A leap year has 366 days instead of 365, with February having 29 days instead of 28. A year is a leap year if divisible by 4, except for century years which must be divisible by 400. So 2024 is a leap year, 1900 was not, and 2000 was. Date calculations must account for this to avoid off-by-one errors.
How many days are in a year?
A common year has 365 days, while a leap year has 366 days. Leap years occur every 4 years (divisible by 4), except for century years (divisible by 100) unless they're also divisible by 400. So 2024 is a leap year, 1900 was not, but 2000 was. The average length of a year in the Gregorian calendar is 365.2425 days. This is important for accurate date calculations spanning multiple years.
How do you count business days between dates?
To count business days (weekdays), calculate the total days between two dates and subtract weekends. For each complete week, there are 5 business days. Count the remaining partial week days individually, excluding Saturdays and Sundays. For example, Monday to the following Friday is 5 business days (but 5 calendar days if same week, or 12 calendar days if next week). Note that public holidays are not automatically excluded unless specifically accounted for.
How many weeks between two dates?
To find weeks between two dates, first calculate the total number of days between them, then divide by 7. For example, 45 days between two dates equals 6 weeks and 3 days (6 complete weeks with a 3-day remainder). If you need only complete weeks, round down. For partial weeks, the remainder tells you the extra days. Our calculator provides both the exact week count and the remaining days.
What is a Date Calculator?
A date calculator is a versatile tool for performing arithmetic with calendar dates. Our date calculator lets you find the exact number of days between two dates or calculate a future or past date by adding or subtracting a specific number of days. Whether you need to determine project timelines, count down to deadlines, or plan events, the date calculator provides instant, accurate results broken down into days, weeks, months, and years.
How to Calculate Days Between Two Dates
To calculate the number of days between two dates manually, follow these steps:
- Count the remaining days in the start month (total days in that month minus the start day)
- Add the total number of days for each complete month between the start and end months
- Add the day of the end date
Example: Days from March 15 to June 10. Remaining days in March: 31 - 15 = 16. Full months: April (30) + May (31) = 61. Days in June: 10. Total: 16 + 61 + 10 = 87 days.
For dates spanning different years, add 365 days for each common year and 366 for each leap year between them. Our Date Calculator handles all of this automatically, including edge cases like leap years and month-end boundaries.
How to Use the Date Calculator
Calculate Days Between Two Dates
- Select the "Days Between" tab
- Enter a start date using the date picker
- Enter an end date using the date picker
- View the result instantly as total days, weeks and days, months and days, or years, months, and days
Add or Subtract Days from a Date
- Select the "Add/Subtract Days" tab
- Choose a starting date
- Enter the number of days to add or subtract
- Toggle between "Add" and "Subtract" mode
- The resulting date is displayed immediately
Common Date Calculations
Here are some frequently needed date calculations for quick reference:
| Scenario | Days |
|---|---|
| 30 days from today | Use Add Days tab |
| 60 days from today | Use Add Days tab |
| 90 days from today | Use Add Days tab |
| 6 months | ~182 days |
| 1 year | 365 or 366 |
Leap Year Rules
Leap years are critical for accurate date calculations. A year is a leap year if it meets these rules:
- Divisible by 4: The year must be evenly divisible by 4 (e.g., 2024, 2028)
- Century exception: If the year is divisible by 100, it is not a leap year (e.g., 1900, 2100)
- 400-year exception: If the year is divisible by 400, it is a leap year despite the century rule (e.g., 2000, 2400)
In a leap year, February has 29 days instead of 28, making the total year 366 days. This means any date calculation that spans February must check whether the year is a leap year to avoid off-by-one errors. Our calculator handles this automatically.
Business Days Explained
Business days (also called working days or weekdays) are Monday through Friday, excluding weekends (Saturday and Sunday). When counting business days between two dates:
- Each complete week contributes exactly 5 business days
- For partial weeks, count only the weekdays (Monday-Friday)
- Public holidays are typically excluded from business day counts but vary by country and region
A standard year has 260 business days (52 weeks x 5 weekdays). After subtracting the 11 US federal holidays, a typical US working year has approximately 249 business days.
US Federal Holidays 2026
The following table lists the 11 US federal holidays for 2026, useful when calculating business days:
| Holiday | 2026 Date | Day |
|---|---|---|
| New Year's Day | Jan 1 | Thursday |
| Martin Luther King Jr. Day | Jan 19 | Monday |
| Presidents' Day | Feb 16 | Monday |
| Memorial Day | May 25 | Monday |
| Juneteenth | Jun 19 | Friday |
| Independence Day | Jul 4 (obs Jul 3) | Saturday |
| Labor Day | Sep 7 | Monday |
| Columbus Day | Oct 12 | Monday |
| Veterans Day | Nov 11 | Wednesday |
| Thanksgiving | Nov 26 | Thursday |
| Christmas | Dec 25 | Friday |
How Days Between Dates is Calculated
The date calculator computes the difference between two dates by converting each date into a timestamp (milliseconds since January 1, 1970) and finding the absolute difference. The result is then converted into calendar units:
- Total Days: The absolute difference in milliseconds divided by the number of milliseconds in a day (86,400,000).
- Weeks + Days: Total days divided by 7, with the remainder as extra days.
- Years, Months, Days: Calendar-aware calculation that accounts for varying month lengths and leap years.
Examples
Days Between January 1 and December 31
From January 1 to December 31 of the same year is 364 days (365 in a leap year). The date calculator breaks this down as 52 weeks and 0 days, or 11 months and 30 days.
Adding 90 Days to a Date
Adding 90 days to March 1, 2025 gives May 30, 2025. This is useful for calculating quarterly deadlines, warranty expiration dates, or trial period end dates.
Common Use Cases
- Project management: Calculate durations and deadlines
- Legal and contractual: Determine notice periods and filing deadlines
- Healthcare: Track treatment cycles and follow-up appointments
- Education: Count school days and semester lengths
- Personal: Plan vacations, count days until events, or track milestones
- Finance: Calculate interest accrual periods and payment schedules
Related Tools
- Countdown Calculator— Count down to a specific date or event
- Age Calculator— Calculate exact age in years, months, and days
- Half Birthday Calculator— Find the date exactly halfway between birthdays
Tips for Using the Date Calculator
- The order of start and end dates does not matter — the calculator always returns a positive difference
- Use the "Add/Subtract" tab to quickly find future or past dates relative to today
- Copy results to your clipboard with a single click for easy sharing
- The "Years + Months + Days" breakdown accounts for calendar-specific month lengths, providing the most human-readable result