Date Difference Calculator
Count the days between two dates, or add and subtract days from any date.
Weekdays count Monday to Friday and don't account for public holidays.
How to use the date difference calculator
This calculator does two jobs. It can count the time between any two dates, and it can add or subtract years, months, weeks and days from a date. Switch between them with the buttons at the top.
Counting the days between two dates
- Choose Between dates.
- Pick a start date and an end date. The end date is set to today by default.
- Tick Include the end date if you want the last day counted as well (see below).
You'll see the gap in years, months and days, plus the total number of days, weeks, months, weekdays and weekend days.
Adding or subtracting from a date
- Choose Add or subtract.
- Pick a start date, then choose Add or Subtract.
- Enter any mix of years, months, weeks and days.
The calculator shows the resulting date and its day of the week. This is perfect for deadlines like "90 days from today" or "6 months before the exam".
Should you include the end date?
By default, the calculator counts the days between two dates, which is how most date maths works. From Monday to Friday of the same week is 4 days.
Sometimes you need to count both the first and the last day, for example when working out the length of a holiday, hotel stay, or a project where you work on both the start and end date. In that case, Monday to Friday is 5 days. Tick the box and the calculator adds that extra day for you.
Rule of thumb: leave the box unticked for "how long until" or "how long since" questions. Tick it when you're counting days you're actually present, working or staying somewhere.
How the calculation works
The total number of days is the simple difference between the two dates on the calendar. Leap years are included automatically, so a period that contains February 29 gets the extra day.
The years, months and days result works like counting on a wall calendar. The calculator first moves forward in whole years, then whole months, and then counts the remaining days. Because months have 28 to 31 days, this is more accurate than dividing the total by 30.
Working days and weekdays
The weekdays figure counts Monday to Friday only. It's a quick way to estimate working days for a project, notice period or delivery time. Remember that it doesn't know about public holidays, which vary by country, so subtract any holidays that fall in your date range.
Adding months: what happens at the end of a month?
Adding a month to January 31 is tricky, because February has no 31st. In these cases the calculator uses the last day of the month instead. So January 31 plus one month gives February 28 (or February 29 in a leap year). This is the same rule used by most banks and spreadsheet programs.
When you enter several units at once, the calculator adds years and months first, then weeks and days. That keeps results predictable and matches how people usually think about dates.
Popular uses
- Countdowns: days until a wedding, holiday, exam or due date.
- Deadlines: find the date 30, 60 or 90 days from an invoice or contract.
- Notice periods: work out your last working day when you resign.
- Relationships and anniversaries: see exactly how long you've been together.
- Pregnancy and baby milestones: count weeks from a start date.
- History and school projects: find how many years separate two events.
Frequently asked questions
How many days are there between two dates?
Choose the "Between dates" mode and enter both dates. The calculator shows the total days instantly, along with the same gap in weeks, months and years.
Does the calculator include the start and end dates?
It counts from the start date up to the end date, so the end date isn't included by default. Tick "Include the end date" to add one day if you need both days counted.
Can it count only working days?
Yes. The weekdays result counts Monday to Friday. It doesn't remove public holidays, so subtract those yourself if any fall within your dates.
What date is 90 days from today?
Switch to "Add or subtract", leave the start date as today, choose Add, and enter 90 in the days box. The result date and its weekday appear immediately.
Are leap years taken into account?
Yes. Every real calendar day is counted, including February 29 in leap years.