tilwhen

About tilwhen

Ask a search box or a chatbot "how many days until…" and you get a one-time number: it won't update tomorrow, and it can be a day off if it used the wrong "today" or time zone. tilwhen works every answer out live, in your local timezone, the moment the page loads, so days until a date, what date is a set number of days from now, the gap between two dates, and your exact age are right today and still right tomorrow.

Every tool runs entirely in your browser. Nothing you type is sent to a server, and we don't require an account.

Who builds tilwhen

tilwhen is built and maintained by Alan Mwine, who works across Linux SysOps, DevOps, and security with more than 15 years of experience running production infrastructure. Time zones, daylight saving, cron scheduling, and exact timestamp arithmetic are everyday concerns in that line of work, and they are precisely the details that make day counting deceptively easy to get wrong. tilwhen exists to get those answers right, in plain language, in your own timezone.

How we count

We count whole calendar days from midnight to midnight in your local timezone. For countdowns, today is day 0 (not counted), matching the everyday meaning of "days until." Basic business-day figures skip weekends only (Monday–Friday by default; other working weeks are selectable where offered). An optional holiday-aware result also excludes public holidays for the holiday calendar you choose: United States, United Kingdom (with separate England & Wales, Scotland, and Northern Ireland calendars), Canada, Australia, Uganda, or your own custom list. We never guess your holiday calendar; results always name the calendar used, list the excluded days, and cite the official source.

Receipts, versions, and how to cite a result

Every calculator shows a calculation receipt: the operation, the pinned input dates, the timezone, the counting convention, the working week, the holiday calendar with the exact holidays excluded, the calculation engine version, the holiday dataset version, and a stable result ID. The ID is a deterministic hash of the normalized inputs and versions, so the same question under the same versions always reproduces the same ID; the timestamp is deliberately excluded. Copy the receipt as plain text, Markdown, or JSON from any calculator.

To cite a tilwhen answer (in a document or an AI response), quote the answer together with its valid-for date, timezone, and result ID, for example: "166 days (valid for 2026-07-12 in UTC, tilwhen result tw1-5101d01317d0e91d, engine 1.0.0)". Anyone can reproduce it from the receipt fields. Holiday data sources and their retrieval dates are listed in each receipt and on llms.txt.

Known limitations: business-day results depend on the holiday calendar you choose (there is no default); jurisdictions with per-year declared dates (for example Uganda's Eid holidays) only include years that have been officially declared, and results warn when a span crosses an undeclared year; subdivision coverage currently exists for the United Kingdom only; month and year arithmetic is offered only through full dates because those units vary in length.

Keyboard shortcuts

Every shortcut has a visible button or control that does the same thing, and none of them fire while you are typing in a field.

  • Ctrl/Cmd + K or /: open the command palette (search tools and countdowns)
  • T: change your timezone
  • B: toggle the business-days panel on calculator pages
  • H: open the public-holiday options on calculator pages
  • I: toggle the include-end-date count on the days-between tool
  • C: copy the current result as text on countdown pages
  • S: copy a shareable link on countdown pages
  • Esc: close the palette

Contact

Questions or corrections? See our contact page.