Date Calculator — Days Between Dates & Date Add/Subtract
Date calculator with days between two dates (workdays included), add or subtract days, weeks, months or years, plus countdowns — all locally in your browser.
Days Between Two Dates
Recalculated as you type · workdays exclude weekends
—
Add to or Subtract from a Date
Months follow calendar months; clamped to month end
Next Holidays
Holiday dates built in · lunar holidays converted from the Chinese calendar
Custom Countdown
Count down to the day that matters to you · one-tap presets included
About this tool
How many days between two dates? What date is 100 days from now? How far away is the next holiday? This date calculator puts the date math people actually need in one place — date difference, workdays, date add/subtract, and a countdown calculator for holidays or your own dates — recalculated as you type, entirely in your browser. Your dates never touch a server.
Two ways to count: including or excluding the end day
"March 1 to March 3" has two common answers:
- Excluding the end day: 2 days (March 1 → March 3 spans 2 day-intervals)
- Including the end day: 3 days (how leave requests and expense reports usually count — the return day counts too)
This tool defaults to excluding the end day; tick "Include end day" to switch, and the day count and week count update together. Agree on the convention before comparing numbers — it is the single most common source of date-counting disputes.
How workdays are counted
Workdays = days in the interval excluding Saturdays and Sundays. Full weeks count as 5 days each; the partial week at either end is judged day by day.
Public holidays and make-up workdays are not yet factored in. For critical deadlines, take the workday result and manually subtract holidays and add back make-up days; a built-in holiday table is on the roadmap.
Add or subtract: days, weeks, months or years
- Days / weeks: pure calendar days, rolling over months and years automatically.
- Months / years: follow calendar months, clamping to month end when the target month has no matching day. Jan 31 + 3 months = Apr 30 (April has no 31st); Aug 31, 2026 + 6 months = Feb 28, 2027. This matches how contracts, visas and probation periods are usually counted.
- For exactly 90 or 180 days, switch the unit to "days".
Common use cases
- Project management: schedule durations and back-planning — which exact day is "freeze requirements 30 days before launch"? Subtract and see.
- Contracts / visas / probation: start date + N months, aligned with calendar-month clauses.
- Study planning: days until the exam, plus a workday estimate of how many days you can actually sit down and study.
- Life milestones: 1000-day anniversaries, weddings, a due date — count down to the day that matters.
- Content scheduling: turn "publish in 7 days" into an actual calendar date, no finger-counting.
Need Chinese dates too? Pair this date calculator with the Simplified-Traditional converter for CJK text, or draft the schedule in the online Markdown editor. More utilities live in the tools channel.
Quick reference table
| Days | Roughly equal to |
|---|---|
| 30 days | 1 month |
| 90 days | 3 months (a quarter) |
| 100 days | 3.5 months |
| 180 days | half a year |
| 365 days | 1 year |
| 1000 days | 2 years 9 months |
To verify the table, use the add/subtract block at the top: base date today, count 100, unit days — the result shows the weekday and the distance from today at once.
FAQ
What does "include end day" mean?
There are two common conventions: excluding the end day (Mar 1 → Mar 3 = 2 days) and including it (= 3 days, the way leave requests often count). This tool defaults to excluding the end day; tick the checkbox to switch.
Do workdays include public holidays?
Workdays here exclude Saturdays and Sundays. Public holidays and make-up workdays are not yet factored in; a built-in holiday table is on the roadmap, which will remove statutory holidays and add back make-up workdays automatically.
Does "3 months later" mean 90 days?
No. It follows calendar months: Jan 31 + 3 months = Apr 30 (April has no 31st, so it clamps to month end), which matches how contracts and visas usually count. For exactly 90 days, pick "days" as the unit.
Does this upload my dates?
No. Everything is computed in your browser — countdowns, anniversaries and birthdays never leave your device, and nothing is stored after you refresh.