The deadline N business days after or before a start date, skipping weekends and the holidays you list, with the calendar days it spans.
10 working days after Sun 27 Sep 2026 is Friday, 9 October 2026 — 12 calendar days later, skipping 2 weekend days.
| Date | Counts as |
|---|---|
| Sun 27 Sep 2026 | Start (not counted) |
| Mon 28 Sep 2026 | Working day 1 |
| Tue 29 Sep 2026 | Working day 2 |
| Wed 30 Sep 2026 | Working day 3 |
| Thu 1 Oct 2026 | Working day 4 |
| Fri 2 Oct 2026 | Working day 5 |
| Sat 3 Oct 2026 | Weekend |
| Sun 4 Oct 2026 | Weekend |
| Mon 5 Oct 2026 | Working day 6 |
| Tue 6 Oct 2026 | Working day 7 |
| Wed 7 Oct 2026 | Working day 8 |
| Thu 8 Oct 2026 | Working day 9 |
| Fri 9 Oct 2026 | Working day 10 |
Start counting on the day after Sun 27 Sep 2026; the start date itself is not counted.
Weekend: Saturday and Sunday.
Friday, 9 October 2026.
Counting starts on the day after the start date. Each day that is neither a weekend day nor a listed holiday counts as one working day, and the nth such day is the deadline; going backwards works the same way from the day before. This is the convention of Excel's WORKDAY functions and NumPy's busday_offset. A holiday that falls on a weekend is skipped once, not twice.
It is used for payment terms, statutory response times, service-level targets and delivery estimates. Five working days after Friday, 18 December 2026, with Christmas Day and New Year's Day listed, is Monday, 28 December, 10 calendar days later. England and Wales also have a bank holiday on 28 December 2026, the substitute day for Boxing Day; list it and the deadline moves to Tuesday, 29 December.
Public holidays differ by country and region, so none are assumed: paste your own, one ISO date per line.
Checked against: numpy.busday_offset('2026-12-18', 5, roll='backward', holidays=[...]) = 2026-12-28; skipped days counted by hand on a 2026 calendar
Checked against: numpy.busday_offset('2026-01-17', 1, roll='backward') = 2026-01-19
Checked against: numpy.busday_offset('2026-01-15', 10, roll='backward', weekmask='1111001') = 2026-01-29
Checked against: numpy.busday_offset('2026-01-15', -10, roll='forward', holidays=['2026-01-01']) = 2025-12-31
Count forward from the next day and skip weekends and public holidays. With no holidays in the way, 10 business days is two full working weeks, so from a weekday it lands on the same weekday 14 calendar days later: 10 business days after Thursday, 15 January 2026 is Thursday, 29 January. Each holiday on a weekday pushes the deadline one working day further.
Not by default. The first working day is the day after the start, the same as Excel's WORKDAY, so 1 business day after a Monday is Tuesday. Some contracts and procedures count the start date as day 1; switch on that option and 10 working days from Thursday, 15 January 2026 ends on Wednesday, 28 January instead of Thursday, 29 January.
Counting still begins with the next working day, so the weekend adds nothing. 1 business day after Saturday, 17 January 2026 is Monday, 19 January, the same answer as from Friday, 16 January. With the start-date option on, a start that isn't a working day can't be day 1, and the calculator warns you.
Between 20 and 23 weekdays before public holidays. February has exactly 20 in a common year and 20 or 21 in a leap year; a 30-day month has 20 to 22 and a 31-day month 21 to 23, depending on the weekday it starts on. A year of 261 weekdays, as in 2026, averages 21.75 per month.
Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 5 worked examples whose answers come from independent sources; for example, “Five working days over Christmas” is checked against numpy.busday_offset('2026-12-18', 5, roll='backward', holidays=[...]) = 2026-12-28; skipped days counted by hand on a 2026 calendar.
Microsoft Excel WORKDAY.INTL function (same convention: the start date is not counted); NumPy busday_offset.
5 worked examples with independently sourced answers ship with this calculator. They run in the test suite; you can run them here too.
The date a number of days, weeks, months, years or business days after or before a start date, with its weekday and the calendar days moved.
Days between two dates, also as years, months and days, weeks and hours, plus business days after weekends and your own holidays.
Exact age from a date of birth in years, months and days on any date, with the next birthday and age in months, weeks, days and hours.
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