Project deadline calculator
Turn a start date plus a number of working days into a deadline, skipping your custom weekly rest days and holidays and showing how many calendar days that spans.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Start date and effort
Saturday and Sunday are rest days by default. The start date defaults to today and is read once after the island mounts. Dates are walked day by day with pure integer arithmetic, so time zones and daylight saving cannot shift the result.
Result
2024-01-0112 days2 days0 days—What this tool does
- Turn a contractual “within 15 business days” into the exact calendar date you can put in the contract.
- Plan a project from today and see at a glance how many weekends and public holidays the schedule crosses.
- Sanity-check a plan against your holiday list before you commit to a date.
- Work backwards: shrink the number of working days until the computed deadline matches a fixed release date.
Example
Input
Start 2024-01-01 (Mon), 6 working days needed, rest days Saturday and Sunday, no holidays
Output
Deadline 2024-01-08; 8 calendar days spanned, 2 rest days skipped, 0 holidays skipped
The start day counts as day 1, so the sixth working day lands on the Monday of the following week. Untick “Count the start day as day 1” and the deadline shifts to 2024-01-09.
Frequently asked questions
What does “Count the start day as day 1” do?
When ticked, the start date counts as day one provided it is a working day, so 2024-01-01 plus 5 working days gives 2024-01-05. When unticked, counting begins the next day and the same 5 working days give 2024-01-08 — which is how most “within N business days” clauses are read.
Can a day be deducted twice as a weekend and a holiday?
No. Each day is tested as a rest day first and then as a holiday, so it is only skipped once. A holiday that happens to fall on a Saturday is simply listed under holiday details rather than being counted twice.
Does it support a six-day week or shift patterns?
Yes. Tick any combination of Monday to Sunday as rest days — Sunday only, or Friday and Saturday, for example — and the count follows your rule exactly.
How far ahead can it calculate?
Up to 10000 working days per run (roughly 38 years); beyond that it reports an error instead of freezing. Dates are walked one day at a time using integer day serials rather than local time, so time zones and daylight saving cannot shift the answer.
Where does “today” come from?
The start date defaults to today, but it is read once after the island mounts. The page does not keep tracking the clock and never sends your dates anywhere.
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