Difference and add/subtract
Switch between counting the gap between two dates and projecting forward or backward from one date, without loading a different page.
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Date Calculator — Days Between Dates, Add or Subtract Time
Count the exact days between two dates, or add and subtract days, weeks, months and years from any date — with working days only, weekend counts and a full years-months-days breakdown.
Difference and add/subtract
Business days only
Leap years handled
Nothing stored
Calculate a date
Pick a mode, enter your dates and get the answer instantly. Everything runs in your browser — nothing is uploaded.
Your result will appear here
Enter your dates and we’ll show the total days, working days, weekends, and the full years, months and days breakdown.
Why this calculator
Two date tools in one, with the details other calculators skip
Counting days is easy to get wrong: leap years, month lengths, whether the last day counts and whether weekends should be excluded all change the answer. This handles every one of them.
Working days, not just days
See how many of the days are weekdays and how many fall on a weekend — and add or subtract in business days when a deadline depends on it.
Every unit at once
One result gives you total days, weeks and days, calendar years-months-days, plus hours and minutes — no second calculation needed.
Inclusive counting option
Contracts, notice periods and hotel stays often count both the first and last day. One toggle switches between the two conventions.
Leap years done properly
February 29 and century rules are handled by real calendar maths rather than dividing by 365, so long spans stay accurate to the day.
Instant and private
Quick buttons for today, +30, +90 and +1 year. No account, no ads over the tool and no dates sent anywhere.
How to use it
How to calculate days between dates in four steps
Choose a mode
Use difference to measure a gap, or add/subtract to project a deadline forward or backward from a known date.
Enter your dates
Type them in or use the quick buttons for today, plus 30, plus 90 or a year ahead.
Set the counting rule
Decide whether the end day counts, and whether weekends should be skipped for business-day maths.
Read the breakdown
You get total days, working days, weekends, weeks, calendar years-months-days and the weekday it lands on.
Benefits
Where an exact date answer actually matters
Most date questions look trivial until money, notice or a legal deadline depends on the answer being right to the day.
Contract and notice periods
Work out the exact end of a 30, 60 or 90-day notice window, including whether the first day counts.
Project deadlines in working days
A ten-working-day turnaround is two calendar weeks, not ten days — and public holidays stretch it further.
Travel and visa windows
Many visas allow a set number of days in a period, and overstaying by one day can carry real consequences.
Returns and warranty periods
Check whether a 14 or 30-day return window is still open before assuming it has closed.
Countdowns and milestones
Days until a wedding, exam, launch or trip — and how many of those are actually working days.
Billing and subscription cycles
Find the precise renewal date when a plan runs for a set number of days rather than a calendar month.
The method
How days between dates are calculated
Counting the days
The difference between two dates is the number of nights between them: 1 March to 10 March is 9 days. Counting both the first and the last day — inclusive counting — gives 10. Neither is more correct; what matters is which convention your contract, visa or booking uses, which is why the tool offers both.
Why you cannot just divide by 365
Years are 365 days except leap years, which have 366. A year is a leap year if it divides by 4, except century years, which must divide by 400 — so 2000 was a leap year and 1900 was not. Over a long span, dividing by 365 drifts by a day for every four years. This calculator uses real calendar arithmetic instead, so the count stays exact.
Working days versus calendar days
A working day is normally Monday to Friday. Over a full week you lose two days to the weekend, so ten working days is fourteen calendar days, and twenty working days is roughly a calendar month. The tool counts weekdays precisely rather than approximating, and can add or subtract in business days too. Public holidays vary by country and region, so subtract those separately for your location.
Quick reference
| Span | Calendar days | Working days |
|---|---|---|
| One week | 7 | 5 |
| Two weeks | 14 | 10 |
| One month (average) | 30 or 31 | 21 or 22 |
| 90 days | 90 | About 64 |
| Six months | 181 to 184 | About 130 |
| One year | 365 or 366 | About 261 |
Adding months is not the same as adding 30 days
Calendar month arithmetic keeps the day number where it exists: 15 January plus one month is 15 February. When the day does not exist in the target month, the result rolls back to the last valid day, so 31 January plus one month becomes 28 February, or 29 in a leap year. Adding 30 days instead would land on 2 March. If a deadline is written in months, use months; if it is written in days, use days.
- Adding one month to the 31st can land on the 28th, 29th or 30th depending on the target month.
- Adding a year to 29 February gives 28 February in a non-leap year.
- Years and months are applied first, then weeks and days, which is the standard order.
- Time zones do not affect whole-date arithmetic, so results are the same wherever you are.
FAQ
Date calculator questions, answered
How do I calculate the number of days between two dates?
Subtract the earlier date from the later one and count the nights in between: 1 March to 10 March is 9 days. If you need both the first and last day included, add one to get 10. Enter your two dates above and the calculator shows both figures along with weeks, months and working days.
What is the difference between calendar days and business days?
Calendar days count every day including weekends. Business or working days count Monday to Friday only, so a week is five business days and ten business days is fourteen calendar days. Public holidays are also excluded in most business-day rules, and those vary by country, so deduct them for your own region.
Should the last day be included in the count?
It depends on the rule you are working to. Hotel stays, notice periods and many contract terms count both the start and end day, while a plain gap between dates does not. Use the inclusive toggle above to switch between the two, and check the exact wording of whatever document the deadline comes from.
How do I add 90 days to a date?
Switch to add or subtract mode, enter the starting date, put 90 in the days field and calculate. The result shows the exact date, the weekday it falls on and how far it is from today. Use the business-days option if the 90 days should skip weekends.
How does the calculator handle leap years?
It uses real calendar arithmetic rather than assuming a fixed 365-day year, so 29 February is counted whenever it occurs. A leap year is any year divisible by 4, except century years, which must also be divisible by 400 — which is why 2000 was a leap year but 1900 was not.
Why does adding one month to 31 January give 28 February?
Because February has no 31st. Standard calendar arithmetic keeps the same day number where it exists and otherwise rolls back to the last valid day of the target month. If your deadline is defined in days rather than months, use the days field instead — 31 January plus 30 days is 2 March.
Can I count how many weekends fall in a period?
Yes. The result breaks the total into weekdays and weekend days, so you can see at a glance how many Saturdays and Sundays sit inside the span. That is useful for scheduling deliveries, planning cover or working out how much of a holiday overlaps a working week.
Get the exact date answer in seconds
Free, private and instant — days between dates, working days, weekend counts and add-or-subtract projections in one place.
This date calculator is provided for general planning and information. Business-day results exclude Saturdays and Sundays but not public holidays, which differ by country and region. Where a deadline is legally or contractually binding, check the exact counting rules in the relevant document or with a qualified professional.