Date Difference Calculator
Find the number of days, weeks, months, and years between any two dates. Add or subtract a number of days to a date. Runs entirely in your browser.
Runs in your browser — nothing uploaded
Pick two dates
Find the exact gap between any two dates — or jump forward or back from a date by a number of days. Handy for project deadlines, lease end dates, gestation tracking, contract terms, and the dozens of everyday questions of the form "what day is 90 days from now?"
Private by design — your data never leaves your device
How to use it
No account, no upload — it all happens on your device.
1
Pick the mode: 'Days between dates' or 'Add or subtract days'.
2
For days between, type two dates — the order doesn't matter, the calculator finds the gap.
3
For add or subtract, pick a starting date, a number of days, and the direction. The result date updates instantly.
4
Scroll down to see the same gap in weeks, business days, hours, and seconds.
What you can answer with this
Two related questions, one tool.
| Question | Mode | Example |
|---|---|---|
| Days between two dates | Days between dates | 1 Jan 2024 → 1 Jul 2024 = 182 days |
| Days until a future date | Days between dates | Today → 25 Dec = 201 days |
| Date N days from now | Add or subtract days | Today + 90 days = exact date |
| Date N days before a deadline | Add or subtract days | Lease end − 60 days = notice date |
Business days vs calendar days
- Calendar days count every day, weekends included. Use these for things like rent, interest, and anniversaries.
- Business days count only Mon–Fri. Use these for shipping windows, contract notice periods, and SLA deadlines. This tool excludes Saturdays and Sundays but does notsubtract public holidays — those vary by jurisdiction and aren't encoded here.
- A common gotcha: a "30 business day" window is about 42 calendar days, since six weekends typically fall inside it.
Pitfalls
- Inclusive vs exclusive counting."5 business days from today" on a Monday usually lands on the following Monday (5 working days after, not including today). This calculator returns the gap between dates — add or subtract a day if your context counts the start.
- Time zones and DST.Dates are interpreted in your local time zone with whole-day arithmetic, so daylight-saving transitions don't change the day count.
- Month math is calendar-based."1 month from 31 January" isn't a single date — there's no 31 February. Use the days input if you need an exact span; use the years/months/days breakdown for human descriptions.
Frequently asked
How does the calculator handle leap years?
The day count is the real number of days between the two dates on the calendar — leap days are counted when they fall in the range. A year-long span that crosses 29 February is 366 days; one that doesn't is 365.
What counts as a business day?
Monday through Friday. Public holidays are not subtracted because they vary by country, state, and even employer — for a holiday-aware count, deduct the relevant holidays from the business-day total.
Does this tool send my dates anywhere?
No. The math runs in your browser as plain arithmetic on the dates you type. Nothing is uploaded, stored, or shared.