Date Difference Calculator
Days, weeks, months & years between two dates
Pick two dates to get the days between them, the exact calendar difference in years, months and days, and a working-day count. This date difference calculator also lets you choose whether both end dates count, because a hire period, a holiday and a notice period are all measured differently.
There are two right answers to "how many days"
From 1 January to 31 December 2026 is either 364 days or 365, and both are correct depending on what you are counting. The gap between the dates is 364. Counting both dates — the first day and the last — gives 365.
The distinction is not pedantry; it decides money. Car hire, hotel nights and interest periods count the gap. Holiday entitlement, notice periods, festival passes and "how many days is my trip" count both ends. Getting days between dates wrong by one is the most common date error there is, so this tool asks rather than picking for you.
A holiday from 6 to 17 July is 11 days as a gap and 12 days counting both — which is the number your employer will deduct from your allowance. The weekday counts follow the same convention: 9 working days as a gap, 10 counting both.
The calendar difference is not days divided by 365
Alongside the day count the calculator gives an exact date duration calculator result in years, months and days, worked out by calendar subtraction rather than division. From 1 January 2000 to 6 September 2026 is 9,745 days, which is 26 years, 8 months and 5 days — not the 26.68 years that dividing by 365.25 suggests.
The approximate rows are still shown because they are genuinely useful for rough comparisons, but they are labelled as approximate for a reason: months have four different lengths and leap years do not distribute evenly.
Working days, and what the count leaves out
The weekday figure counts Monday to Friday only. It is calculated by taking whole weeks at five weekdays each and walking only the leftover days, so a span of decades costs no more effort than a span of days.
| Period | Days | Weekdays | Weekend days | Calendar difference |
|---|---|---|---|---|
| 1 Jan – 1 Mar 2026 | 59 | 41 | 18 | 2 months |
| 1 Jan – 31 Dec 2026 | 364 | 260 | 104 | 11 months, 30 days |
| 1 Feb – 1 Mar 2026 | 28 | 20 | 8 | 1 month |
| 1 Feb – 1 Mar 2028 (leap) | 29 | 21 | 8 | 1 month |
| 1 Jan 2000 – 6 Sep 2026 | 9,745 | 6,960 | 2,785 | 26 years, 8 months, 5 days |
Counting the gap between the dates, not both ends.
Public holidays are not deducted. They vary by country, state and sometimes employer, and a tool that silently applied one country's calendar would be wrong for most people using it. If you need true business days, take the weekday figure and subtract the holidays that actually apply to you.
Why a leap year changes the answer
February 2026 is 28 days; February 2028 is 29. That single day is why any date calculation spanning a February needs the real calendar rather than a fixed month length, and why "a month" is not a fixed quantity.
The rule itself is more than "every four years": a year is a leap year if it divides by 4, except centuries, unless they divide by 400. 1900 was not a leap year; 2000 was. Spans crossing 1900 catch out a surprising amount of software, and it is worth checking any tool you rely on against a date you know.
Where date differences go wrong
- Off-by-one from the wrong convention. The single most common error, and the reason the counting method is an input here rather than an assumption.
- Time zones. Tools working in UTC can be a day out either side of midnight. This one compares calendar dates in your local time.
- Treating a month as 30 days. Fine for a rough figure, wrong for contracts. Use the calendar difference for anything that matters.
- Assuming weekdays means working days. Weekday counts ignore public holidays entirely, and in some sectors ignore shift patterns too.
- Daylight saving. Not a factor here, because whole calendar dates are compared rather than elapsed hours — but it does break any tool that subtracts timestamps.
A date-arithmetic tool. For contractual or legal deadlines, confirm the counting convention that applies.
How this date difference calculator works out its numbers
Days are the whole-day difference between the two dates, with one added when both ends are counted. Weekdays are found by taking whole weeks × 5 and walking only the remaining days from the first counted date, so the cost does not grow with the span. The calendar difference uses year, month and day subtraction with borrowing, exactly as the age calculator does.
- The counting convention is an input, not an assumption. The gap and both-ends answers differ by one day, and which is correct depends entirely on what is being measured.
- Public holidays are never deducted. They differ by country, state, sector and employer; applying any single calendar would be wrong for most users, so the weekday count is Monday to Friday and nothing else.
- Dates are compared as local calendar dates, constructed at local midnight, so time zones and daylight saving cannot shift the answer.
- Approximate months use 30.44 days (365 ÷ 12) and approximate years use 365.25. Both are labelled approximate; the calendar difference is the exact figure.
- Order does not matter. Dates entered backwards are swapped, so the result is never negative.
Reviewed September 2026.
Figures reviewed . Every worked example on this page is checked against the calculator above.
Date Difference Calculator: frequently asked questions
How do I calculate the number of days between two dates?
Subtract the earlier date from the later one. From 1 January to 31 December 2026 the gap is 364 days, or 365 if you count both the start and end dates — pick the convention that matches what you are measuring.
Should I count both the start and end date?
It depends. Car hire, hotel nights and interest periods use the gap. Holiday entitlement, notice periods and trip lengths count both ends. A 6–17 July holiday is 11 days as a gap and 12 counting both.
How many working days are between two dates?
The calculator gives a Monday-to-Friday count — 260 weekdays in 2026 measured as a gap. Public holidays are not deducted, because they vary by country, state and employer, so subtract the ones that apply to you.
Why isn't the answer just days divided by 365?
Because months have four different lengths and leap years land unevenly. From 1 January 2000 to 6 September 2026 is 9,745 days, which is exactly 26 years, 8 months and 5 days rather than the 26.68 years division suggests.
How many days are in a month?
Between 28 and 31, which is why the tool shows an exact calendar difference alongside the approximate months figure. The approximate row uses 30.44 days, the average month length across a full year.
Does this account for leap years?
Yes, automatically. February 2026 has 28 days and February 2028 has 29, and both are counted correctly. A leap year is any year divisible by 4, except centuries, unless they divide by 400.
How many weeks between two dates?
Days divided by seven — 52 weeks for the 364-day gap across 2026. It is shown to one decimal, since most spans do not land on a whole number of weeks.
Can time zones change the result?
Not here. Both dates are compared as local calendar dates rather than timestamps, so the answer does not shift near midnight or across daylight saving changes.