Custom Holiday Business Day Calculator
Bring your own holidays — exclude any list of dates from counts.
Written and maintained by Paul Clark, Redmoon Software · Rules last verified
These calculators are for informational purposes only and do not constitute legal, financial, or professional advice.
How the Custom Holiday Business Day Calculator works
The Custom Holiday Business Day Calculator counts working days across a range using your own closure list on top of a national holiday calendar — and then tells you how much your list actually changed the answer. That second part is the reason this tool exists separately from a plain business-day count.
Paste in company shutdown dates, regional observances your country calendar does not carry, floating holidays, or site-specific closures, and the calculator reports four numbers: the working days with your list applied, the working days without it, how many of your dates fell inside the range at all, and how many of those actually removed a working day. That last figure is usually smaller than people expect, because closure lists are full of dates that land on a weekend or duplicate a public holiday already in the calendar. A twelve-date shutdown list that removes four working days is doing far less than its length suggests, and knowing which is which is the difference between a schedule you can defend and one you have padded twice.
The redundancy count is diagnostic rather than a warning — a Christmas shutdown legitimately overlaps public holidays, and that overlap is exactly what you want to see quantified rather than double-counted. Dates outside the range are reported separately and ignored in the maths, which catches the common paste error of bringing in a whole year of company closures when the range covers one month. Format the list one date per line or comma-separated in YYYY-MM-DD; anything unparseable is skipped rather than silently treated as a closure.
Worked example
A June 2026 range under a US calendar holds 21 working days once weekends and the Juneteenth holiday are removed. Paste in a six-date company closure list and the count drops to 17 — but the calculator shows that only four of the six dates were inside the range and actually removed a day. The other two were a Saturday and Juneteenth itself, already excluded. Without that breakdown you would believe the shutdown cost six days when it cost four.
Frequently asked questions
Why does it tell me some of my dates were redundant?
Because closure lists routinely contain dates that were never working days — weekends, and public holidays the country calendar already removes. Those dates cost you nothing, and counting them as if they did inflates the perceived impact of a shutdown. Seeing the effective count separately from the supplied count tells you what your list is really worth.
What format should the closure list be in?
ISO dates — YYYY-MM-DD — one per line or separated by commas or spaces. Anything that does not parse is skipped rather than guessed at, so a malformed entry will quietly not be applied; if the effective count looks lower than you expected, check the formatting of the list first.
Can I use this instead of selecting a country?
You can — set the country to none and supply every non-working day yourself, which is the right approach for an organisation whose calendar does not match any national one, or for a country the tool does not carry. The trade-off is that you then own the completeness of the list, including any holiday that moves year to year.
What this calculator does not do
A limitation you know about costs far less than one you find after the deadline. These are the specific things this tool cannot work out for you.
- Custom dates are treated as full non-working days. A half-day closure cannot be expressed.
- Custom dates are added to whichever country calendars you have selected, not used in place of them. Deselect the countries if you want your list alone to govern.
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