Date Difference Calculator
Days between two dates, split into weekdays and weekends, plus date arithmetic.
Counting days across a calendar by hand goes wrong in predictable places: the month with 31 days, the leap February, and the question of whether the last day counts. This calculator handles all three, splits the total into weekdays and weekend days for anything measured in working time, and can also add or subtract a number of days from a date.
How it works
Set the two dates
In either order — a negative span is reported rather than rejected.
Decide whether the last day counts
Contracts and notice periods usually include it; durations usually do not.
Or do date arithmetic
Add or subtract days from a date and get the weekday it lands on.
Whether the last day counts changes the answer by one
From 1 March to 8 March is seven days if you are measuring a duration and eight if you are counting days affected. Both are used constantly, and neither is more correct — they answer different questions. A hotel stay of seven nights spans eight dates; a seven-day notice period usually means seven clear days after the notice.
Legal and contractual deadlines have their own conventions on top of this. Many jurisdictions exclude the day an event happened and include the day the period ends, which is the "clear days" rule. Others count both. If a deadline matters, the contract or statute will say which — and if it does not, the difference of one day is exactly the kind of ambiguity that ends up being argued about.
The checkbox here makes the choice explicit rather than picking one silently. Left unticked, the result is the plain interval: the number of midnights between the two dates. Ticked, it counts both endpoints, which is what you want for "how many days does this cover".
Weekdays, working days, and why they are not the same
The weekday count here excludes Saturdays and Sundays and nothing else. That makes it a starting point for a working-day calculation, not a finished one — public holidays vary by country, by region within a country, and by year, and there is no universal list to apply.
The gap is larger than it looks. A calendar year holds about 261 weekdays; subtract public holidays and the working total lands closer to 250 in most of Europe, and lower again in countries with more of them. Over a 90-day project window that is typically three or four days of difference, which is enough to move a delivery date.
The weekend itself is not universal either. Friday and Saturday are the weekend across much of the Middle East, and a few countries observe a single rest day. If you are scheduling across regions, the weekday figure here reflects the Monday-to-Friday convention and will need adjusting — the plain day count is the neutral figure to work from.