How to Calculate Days Between Two Dates
How many days until a deadline? How many weeks between two events? How many months until a contract expires? Date math sounds simple until you factor in months with different lengths, leap years, and whether to count the start or end date.
How to calculate days between dates
- Select your start date — pick the earlier date using the date picker.
- Select your end date — pick the later date.
- Read the result — see the total number of days, plus a breakdown in years, months, weeks, and days.
Adding or subtracting days
The calculator also works in reverse: start with a date and add or subtract a number of days to find the resulting date.
Example: What date is 90 days from March 1, 2026? The answer is May 30, 2026.
This is useful for:
- Contract deadlines — "payment due within 30 days"
- Notice periods — "60 days notice required"
- Planning — "the event is 120 days away, what date is that?"
Common date calculations
| From | To | Days |
|---|---|---|
| Jan 1 | Dec 31 | 364 (365 in leap years) |
| Jan 1 | Jun 30 | 180 (181 in leap years) |
| Any date | Same date + 1 year | 365 (or 366) |
| Any date | Same date + 1 quarter | 90-92 |
Tips
- Business days vs calendar days — the calculator counts calendar days (including weekends and holidays). If you need business days, subtract weekends manually or note that roughly 5/7 of calendar days are business days.
- Include or exclude endpoints — "days between" gives you the gap. If a contract says "within 30 days including today," you may need to add 1.
- Use date math for project planning — enter your project start date and add the estimated number of days to find your target completion date.
- Works on any device — the calculator runs in your browser on desktop, tablet, or phone with no installation needed.
Frequently Asked Questions
Does the calculation include the start and end dates?
The calculator counts the days between the two dates. If you need to include both the start and end date in the count, add 1 to the result.
Can I add or subtract days from a date?
Yes. The date calculator has a mode where you enter a starting date and a number of days to add or subtract, giving you the resulting date.
Does it account for leap years?
Yes. The calculation uses actual calendar dates, so February 29 in leap years is handled correctly.
Can I calculate weeks and months too?
Yes. The result shows the difference broken down into years, months, weeks, and days so you can read it however you prefer.