Time between two dates
The order does not matter — put them in either way round.
Add or subtract time
Where a date lands a set period before or after a starting point.
What the two checkboxes do
Counting the end date
This is the single most common source of confusion in date arithmetic. Monday to Friday is four days if you are measuring elapsed time, and five if you are counting the days themselves — as you would for a five-day event or a five-night stay. Contracts, hire agreements and notice periods differ in which they mean, so read the wording before relying on either figure.
Working days
By default the working-day count covers Monday to Friday. Since the working week is not the same everywhere, Saturday can be switched on for regions and industries where it is a normal working day.
Public holidays are not deducted, because they differ by country, by region within a country, and by year. If your span crosses holidays you know about, subtract them from the working-day figure yourself.
Where this gets used
Project planning is the obvious case: how many working days actually sit between today and a deadline, which is usually a smaller number than the calendar suggests. Payment terms written as net 30 or net 60 need the same arithmetic. Notice periods, probation periods, warranty windows, visa validity and return policies all run on counted days. On the personal side, the same calculation answers how long until an event, or how long since one.
The second panel handles the reverse question. Given a start date and a duration, it returns the date you land on — useful for working out when a 90-day period expires, when a contract ends, or what date falls six months from signing. The day of the week comes with it, since a deadline landing on a Sunday usually needs moving.
How the calendar is handled
Every calculation uses real calendar dates, so leap years are included wherever they fall and month lengths are counted as they actually are. When you add months to a date near the end of a month, the result follows standard calendar behaviour: adding one month to 31 January lands in early March, because February has no 31st. Spreadsheets and date libraries behave the same way.
Frequently asked questions
Does the order of the dates matter?
No. If the end date falls before the start date, the two are swapped automatically and the duration is reported as a positive figure.
Are public holidays excluded from working days?
No. Holidays vary too much between countries, regions and years to apply reliably, so only weekends are excluded. Subtract any holidays in your span by hand.
Why does adding one month to 31 January give a date in March?
Because February has no 31st, so the extra days roll into the following month. This is the standard behaviour in spreadsheets and date libraries alike.
Can I use this to work out an age?
You can, though the age calculator is built for it and adds a birthday countdown and total time lived.
Are my dates stored anywhere?
No. Everything is calculated in your browser and nothing is transmitted.