Before you start
Project Date Calculator
Work out a finish date, the latest start that still meets a deadline, or the working days between two dates, on your own workweek and holidays. Or check a list of milestone dates for the ones that land on a day nobody works.
Type dates in, paste a list, or read a .xlsx or .csv inside your browser. Nothing is uploaded.
Working calendar Monday to Friday, US federal holidays, weekend holidays moved to the nearest working day change
A five-day task starting Monday finishes Friday, and also next Monday
Scheduling software counts the start date as the first day of the work, so a five-day task that starts Monday finishes Friday. “Five working days after Monday” is the following Monday. Both are correct and they answer different questions: one is when the work is done, the other is when a promise of five working days comes due. The tool shows both, labeled, because a plan built on one and a contract built on the other disagree by a day without anybody noticing.
Working back from a date that cannot move
Most plans are built backward from a date somebody has already announced. The latest start is the last day a task can begin and still finish by the deadline, with nothing spare. If the deadline is itself a day nobody works, the work has to be finished on the working day before it, and the tool says so rather than quietly assuming the weekend is available.
Whose calendar
A working-day count with no holidays in it is a weekday count, and over a year the two differ by ten or eleven days. Nothing is assumed: the calendar is shown at the top of every result, the US federal and England and Wales lists are offered as starting points and labeled as exactly that, and company shutdowns can be pasted in. Teams that work Sunday to Thursday, or six days a week, choose their own workweek.
A holiday that lands on a weekend
In 2026 Independence Day is a Saturday. Whether the office closes on Friday the 3rd is a policy somebody decided once and probably did not write down, and it moves every date that crosses it. You can move such holidays to the nearest working day, always forward, or not at all. The UK list already carries the substitute days the rules set.
Milestones on days nobody works
A go-live on Christmas Day or a sign-off on Labor Day is usually a date typed into a spreadsheet without a calendar beside it. Paste the list or load the file and every date is checked, with the working days either side. The date order is settled by the file itself: a 26 in the second place proves the dates are written month first. When nothing in the column can settle it, the tool asks rather than guessing, because 03/04/2026 is two different days.
What this does not do
It counts whole working days on one calendar. It does not schedule dependent tasks, level resources, handle part days or time zones, or know your organization’s policies. A milestone on a weekend is flagged, not forbidden: whether a weekend cutover is a mistake or the plan is a decision for the people running it.