Date Difference Calculator
Difference between two dates
Add or subtract days from a date
This free Date Difference Calculator tells you exactly how much time sits between any two dates, and it can also add or subtract days from a date to find a new one. The difference is shown in three useful ways at once: a friendly years, months and days breakdown, the exact total number of days, and the same span expressed as weeks plus leftover days. That makes it handy for counting down to a wedding or holiday, working out an age in days, checking how long a project ran, or finding a deadline that is a fixed number of days away.
The second tool handles the other common date question: what date is it thirty, ninety or any number of days from now, or before a given day. It correctly rolls across month ends, leap years and year boundaries, and it names the weekday of the result, which is useful when planning around weekends. Everything runs locally in your browser, so the dates you enter are never uploaded or stored anywhere. If you enter the end date before the start date, the tool simply swaps them and tells you, instead of showing a negative answer.
How to use
- For a difference, pick the start date and the end date in the first card.
- Click Calculate difference and read the breakdown, total days, and weeks.
- To shift a date, use the second card and choose any starting date.
- Type the number of days, choose Add or Subtract, then click the button.
- Read the resulting date together with its day of the week.
Frequently asked questions
Does the calculator count both the first and last day?
It measures the standard difference between the two dates, so from Monday to Tuesday is one day. If you need an inclusive count for things like hotel nights or leave forms, simply add one day to the total shown.
How are months handled when the days do not line up?
The breakdown borrows days from the previous month when needed, the same way people normally work out an age. A span such as January 31 to March 1 is therefore expressed sensibly rather than as a negative number of days.
Does it understand leap years?
Yes. The calculation uses real calendar dates, so February 29 in a leap year is counted correctly, and long spans that cross several leap years stay accurate.
Can I calculate dates far in the past or future?
Yes, the date boxes accept any year your browser allows, so historical spans and long-term planning dates both work the same way.
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