Date Calculator
Three modes in one calculator: how many days between two dates, what date is X days from a given date, and a live ticking countdown to any future date. The URL hash is your save state.
What this calculator does
- Days between — type two dates, see days, weeks + days, months + days, years + months. Optional inclusive count, business-days-only mode, and US-federal-holiday exclusion.
- Add / subtract days — pick a start date and a number of calendar or business days; see the resulting date and what day of the week it falls on.
- Live countdown — pick a future date and watch the days/hours/minutes/seconds tick down in real time. Past dates show elapsed time.
Why "days between" is harder than it looks
Many calculators get the basic count right but mess up the human-readable breakdown. The questions the math has to answer:
- Are we counting calendar days or 24-hour spans? April 1 → April 2 is "1 day" if you count midnights crossed, but "24 hours" of elapsed time. This calculator counts midnights — the standard interpretation.
- What about months? "1 month" doesn't have a fixed length. Jan 31 → Feb 28 is 28 days, not "0 months 28 days." This calculator uses the calendar definition: same day next month + remainder days.
- Leap years? Handled — Feb 29 → Feb 28 next year is "364 days, 11 months 30 days, 0 years 11 months."
Common use cases
- Project deadlines — pick "Add days" mode, type the kickoff date, and add 30 / 60 / 90 to see milestone dates.
- Vacation accruals — turn on "include end date" for inclusive counting that matches HR systems.
- Wedding / birthday countdowns — copy the share link, drop it on a Slack channel, watch it tick.
- Visa / lease expirations — both date math and the days-until ticker for a single page reference.
- "Days since last X" — pick a past date in countdown mode; it tracks elapsed time.
Sharing a scenario
Every input is encoded in the URL hash. Bookmark a countdown URL and the calculator state restores when you visit. Share it with a colleague and they see your exact two dates without retyping.
What this calculator does not do
- Non-US public holidays — business-day mode can skip US federal holidays, but other jurisdictions' calendars aren't built in.
- Timezone-aware — all math runs in UTC. If you need to know "what day is X in Tokyo when it's Y in NYC," that's a separate (harder) problem; consider epoch.tooljo.com for timezone conversion.
- Recurring schedules — "every other Tuesday for 12 weeks" needs an iterator, not a date math tool.
For developers
The math is the standard JS Date API run in UTC midnight to avoid DST
drift. If you need this logic in code: new Date(Date.UTC(y, m-1, d))
for both endpoints, then (b - a) / 86_400_000. Read more
about the gotchas in our five
timestamp formats that bite post.
FAQ
Is anything I enter sent to a server?
No. All math is in your browser — open DevTools → Network and confirm. The URL hash carries the inputs but never leaves your machine.
How is 'business days' calculated?
Monday through Friday only — weekends excluded. The count is start-date inclusive and end-date exclusive (Mon → next Mon = 5 business days). Tick also skip US federal holidays to exclude US holidays as well; other countries' holidays aren't included, so subtract those manually.
Which holidays does 'skip US federal holidays' exclude?
The 11 US federal holidays, computed by rule for any year: New Year's Day, MLK Day (3rd Mon Jan), Washington's Birthday (3rd Mon Feb), Memorial Day (last Mon May), Juneteenth (Jun 19), Independence Day (Jul 4), Labor Day (1st Mon Sep), Columbus Day (2nd Mon Oct), Veterans Day (Nov 11), Thanksgiving (4th Thu Nov), and Christmas (Dec 25). Fixed-date holidays follow the federal observed rule: if the date lands on a Saturday the Friday before is excluded, on a Sunday the Monday after. So July 4, 2026 (a Saturday) excludes Friday July 3. State holidays and stock-market-only closures are not included.
What date is 30 business days from today?
Use Add / subtract days mode, switch the unit to Business days, and enter 30 (the +30 preset works too). The calculator steps day by day, skipping Saturdays and Sundays — and US federal holidays if that box is ticked. The start date itself isn't counted, and negative numbers walk backwards (−10 business days = 10 working days earlier).
Why does the live countdown say a date is 'past'?
If the target date is in the past, the countdown shows the elapsed time since it. Useful for anniversaries, project anniversaries, or 'days since last incident'-style counters.
What's the 'Include the end date' option for?
If you check it, the count is inclusive — it counts both the start and end dates. Inclusive counts are common when computing service days, vacation balances, or rental periods. Default is exclusive (end - start), which is the right answer for 'how many days from now until X'.
Does this handle leap years and DST?
Yes. All math is done in UTC at midnight, so daylight saving transitions don't sneak in. Leap years are accounted for in the day-count and the month/year breakdown.