Date Calculator Add and Subtract Days
Date Calculator
Date Selection
Date Difference Results
Enter valid dates to calculate the difference
The date calculator finds the number of days, weeks, months, or years between two dates. It also adds or subtracts a number of days from any date to find a future or past date. Use it for deadlines, project planning, contract durations, and legal date calculations.
Days Between Two Dates
To count the days between two dates, the calculator counts every calendar day including the start date. Leap years add an extra day (February 29) to the count for any span that includes them. The result can be expressed in total days, weeks and days, or months and days.
Days = End Date - Start Date (counting each calendar day)
Example: January 1 to March 31 = 89 days in a non-leap year, 90 days in a leap year.
Adding or Subtracting Days from a Date
To find a date a certain number of days in the future or past, add or subtract the number of days while accounting for month lengths and leap years. Adding 90 days to March 1 lands on May 30 (non-leap year) or May 29 (leap year). This is useful for calculating contract end dates, payment due dates, and legal notice periods.
Business Days vs. Calendar Days
Business days exclude weekends (Saturday and Sunday) and sometimes public holidays. A 10-business-day window starting Monday, March 3 ends on Friday, March 14 (skipping two weekends). Legal and financial contracts often specify business days rather than calendar days. This calculator can count both.
Common Date Calculation Reference
| Period | Calendar Days | Business Days (approx.) |
|---|---|---|
| 1 week | 7 | 5 |
| 2 weeks | 14 | 10 |
| 1 month (avg) | 30-31 | 21-23 |
| 3 months | 90-92 | 65-67 |
| 6 months | 181-184 | 130-132 |
| 1 year | 365 (366 leap) | 260-262 |
Frequently Asked Questions
How do I calculate the number of days between two dates?⌄
Subtract the earlier date from the later date. In practice, convert both dates to a day count from a fixed reference point, then subtract. This calculator handles all the edge cases including month lengths and leap years automatically.
How many days until a specific date?⌄
Enter today's date as the start date and your target date as the end date. The calculator will count the exact number of days remaining. For example, the number of days until December 31 from today.
What date is 90 days from today?⌄
Enter today's date and add 90 days. The result depends on the current month. From January 1, 90 days lands on April 1. From March 1, it lands on May 30 (or May 29 in a leap year). Use the date calculator for the exact result.
How many days are in a year?⌄
A standard year has 365 days. A leap year has 366 days. Leap years occur every 4 years, except for century years that are not divisible by 400. So 2000 was a leap year, but 1900 was not.
How do I calculate a contract end date?⌄
Enter the contract start date and add the contract duration in days. For a 1-year contract starting July 1, 2024: add 365 days = July 1, 2025 (or 366 if spanning a leap year). For month-based contracts, add the number of months instead of days to land on the same day of the end month.