Date Difference Calculator
Count the days, weeks, months and years between two dates, or add and subtract days from any date.
About the Date Difference Calculator
This date difference calculator counts the exact time between any two calendar dates — broken down into years, months and days, plus the total number of days and weeks. Pick a start and end date and the result appears instantly, correctly accounting for leap years and months of different lengths.
A second section lets you add or subtract any number of days from a date. Enter a start date, choose add or subtract, type the number of days, and the tool returns the resulting calendar date, including the day of the week. That makes it easy to answer questions like "what date is 90 days from today?" or "what was the date 45 days ago?"
It is useful for project deadlines and notice periods, visa and passport validity, pregnancy and medical follow-ups, loan and subscription periods, countdowns to events, and legal or contractual date maths. All calculations happen locally in your browser, so nothing you enter is stored or shared.
How to Use the Date Difference Calculator
- 1Choose a start date and an end date in the first section.
- 2Read the difference in years, months and days, plus total days and weeks.
- 3To project a date, use the second section: pick a date, choose add or subtract, and enter the number of days.
- 4The resulting calendar date, with its weekday, appears instantly.
Frequently Asked Questions
How are days between two dates counted?
The calculator measures the exact span between the two dates and reports it two ways: as a calendar breakdown (complete years, then months, then days) and as a simple total-day count. Leap years and 28-, 30- and 31-day months are all handled automatically, so the answer is exact.
Does the count include both the start and end dates?
The tool counts the elapsed time between the dates, so Monday to Friday of the same week is 4 days. If you need an inclusive count — where both endpoints are counted, as in some rental or dosing calculations — simply add 1 to the total-days result.
How do I find the date 90 days from today?
Use the add/subtract section: leave the start date as today, select "Add days", and enter 90. The calculator rolls the calendar forward correctly across month and year boundaries and shows the exact resulting date along with the day of the week.
Why is the months figure not just total days divided by 30?
Because calendar months have 28 to 31 days, dividing by 30 gives only an approximation. This calculator walks the actual calendar: it counts complete months from the start date, then the leftover days. That is why January 31 to March 1 shows 1 month and 1 day, not "0.97 months".
Can I calculate working days or business days between dates?
This tool reports total calendar days and full weeks. For a quick business-day estimate, take the total weeks × 5 and adjust for the leftover days and any public holidays in your region. A span of 30 days, for instance, contains roughly 22 working days.