date ± days · A → B
Date calculator
There are 364 days between 1 January 2026 and 31 December 2026, or 365 when both end days are counted. Enter two dates to count the days between them, or one date and a span to add or subtract.
- 2026-01-01 → 2026-12-31 = 364 d
- 2024-02-29 + P1Y = 2025-02-28
- 2026-01-31 + P1M = 2026-02-28
Results update as you type. Weekdays mean Monday to Friday; public holidays are not taken out because they differ by country and year. Nothing you enter leaves this page.
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At a glance
- Price
- No charge
- Account
- None needed
- Upload
- Not applicable — you type dates, nothing is sent anywhere
- Calendar
- Proleptic Gregorian, years 1 to 9999, counted in UTC
- Month ends
- 31 January + 1 month = 28 February (29 in a leap year)
- Weekdays
- Monday to Friday; public holidays are not removed
Leap years and month ends
These tables are computed with the same rules as the calculator. A tick means the year is divisible by that number.
| Year | Divisible by 4 | Divisible by 100 | Divisible by 400 | Days in the year |
|---|---|---|---|---|
| 1900 | ✓ | ✓ | – | 365 |
| 2000 | ✓ | ✓ | ✓ | 366 |
| 2023 | – | – | – | 365 |
| 2024 | ✓ | – | – | 366 |
| 2100 | ✓ | ✓ | – | 365 |
| Start date | Plus 1 month |
|---|---|
| 2026-01-29 | 2026-02-28 |
| 2026-01-30 | 2026-02-28 |
| 2026-01-31 | 2026-02-28 |
| 2024-01-31 | 2024-02-29 |
| 2026-03-31 | 2026-04-30 |
| 2026-08-31 | 2026-09-30 |
How to use the date calculator
Pick a mode
Choose days between to measure the gap from one date to another, or add or subtract to move a date forward or back by years, months, weeks and days.
Enter the dates
Use the date pickers, or type a date as YYYY-MM-DD, for example 2026-12-31. For a count that includes both the first and the last day, tick the box under the dates.
Read the result
The days between appear as a plain number, as weeks and days, as years, months and days, and as weekdays. When you add or subtract, you get the new date, its weekday and its ISO week.
How the dates are counted
Every date is turned into a whole day number on the Gregorian calendar, in UTC, so a daylight saving change or your time zone can never move a result by a day. The days between two dates are the difference of those numbers: 1 January 2026 to 31 December 2026 is 364. Counting both end days adds 1, which gives 365. Weekdays are the Monday to Friday days in the span; the calculator does not know your public holidays, so subtract them yourself.
When you add months, the day of the month is kept, unless the target month is shorter, in which case the last day of that month is used: 31 January plus 1 month is 28 February (29 in a leap year), and 29 February 2024 plus 1 year is 28 February 2025. Years and months are applied first, then weeks and days. The years, months and days between two dates use the same rule: whole months that fit, then the days left over. Dates run from 0001-01-01 to 9999-12-31 in the proleptic Gregorian calendar, which extends today's leap-year rules backwards and ignores older calendars.
Date calculator questions
How many days are there between two dates?
Subtract the earlier date from the later one. From 1 January 2026 to 1 January 2027 is 365 days, and from 4 July 2026 to 25 December 2026 is 174 days. The calculator also gives the same gap as weeks and days, as years, months and days, and as weekdays.
Do I count the first day and the last day?
It depends on the question. The difference between 1 January and 31 December 2026 is 364 days, which is how many days pass from the first date to the second. If you want the number of calendar days on which something takes place, both end days count and the answer is 365. Tick the box to switch.
What is 90 days from today?
Choose add or subtract, keep today's date as the start, enter 90 in the days field and read the date. For example, 90 days after 1 January 2026 is 1 April 2026. Use the subtract option to go back instead.
What happens when I add a month to 31 January?
February has no 31st, so the result is the last day of February: 28 February 2026, or 29 February in a leap year such as 2024. In the same way, 31 March plus one month is 30 April.
Does the calculator count business days and holidays?
It counts weekdays, Monday to Friday, and treats every one of them as a working day. For 5 January to 30 January 2026, counting both ends, that is 20 weekdays. Public holidays are not included because they depend on the country, the region and the year, so subtract the ones that apply to you.
How do I know if a year is a leap year?
A year is a leap year when it is divisible by 4, except for century years, which must be divisible by 400. So 2024 and 2000 are leap years with 366 days, while 1900 and 2100 are not. Leap years add 29 February.