Count the days between two dates, add days to any date, or find out what date it will be 30, 45, 90 or 180 days from today. Pick your dates and the answer appears straight away — the count is end date minus start date, so 1 January to 2 January is 1 day. It runs entirely in your browser: free, instant, no sign-in.
How the date calculator works
The maths is simple subtraction and addition on the calendar. Days between two dates = end date − start date. 1 January 2026 to 1 February 2026 is 31 days, because January has 31 days. The count does not add the end date on top: 1 January to 2 January is 1 day, not 2. Adding days moves forward on the calendar by that many days — 1 November 2026 plus 30 days is 1 December 2026 — and subtracting moves backwards the same way. Leap years are handled automatically: 28 February 2028 plus 1 day is 29 February 2028, because 2028 is a leap year, while 28 February 2027 plus 1 day is 1 March 2027. All dates are counted as whole calendar days, so daylight-saving changes can never shift the answer by a day.
Some dates matter more than others: the day a deadline falls, the day a holiday starts, the day 30 days from now lands. The Date Calculator answers those questions in seconds. Count the days between two dates, add or subtract days from any date, or find out what date it will be 30, 45, 90 or 180 days from today. The count is end date minus start date — 1 January to 2 January is 1 day — so the answer matches the way most people count days on a calendar, and leap years and daylight-saving changes are handled automatically.
The calculator runs entirely in your browser, so nothing you enter is uploaded anywhere, and there is no sign-in and no limit on how often you use it.
How to use the calculator, step by step
There are three modes. Pick the tab that matches your question.
- Step 1 — Days between two dates. Pick a start date and an end date from the date pickers. The calculator shows the number of days between them, and the same span in weeks and days. 1 January 2026 to 1 February 2026 is 31 days — 4 weeks and 3 days. If the end date is before the start date, the count comes out negative and the calculator tells you how many days earlier it is.
- Step 2 — Add or subtract days. Pick a start date, choose “Add days” or “Subtract days”, and enter how many days. 1 November 2026 plus 30 days is 1 December 2026; 1 November 2026 minus 30 days is 2 October 2026. The result shows the new date and the maths behind it.
- Step 3 — Days from today. Open the “Days from today” tab and the calculator shows 30, 45, 90 and 180 days from today in one list, each with its resulting date. It uses your device’s current date, so the answers are always up to date.
- Clear and start again. The Clear button on the first two tabs empties the inputs so you can run a new calculation without refreshing the page.
How the maths works
A date calculator only needs two operations — subtraction and addition on the calendar — but the calendar has a few quirks: months have different lengths, February gains a day in leap years, and clocks jump forward and back for daylight saving. The calculator counts whole calendar days, so none of those quirks can shift the answer.
- Days between two dates = end date − start date. 1 January 2026 to 1 February 2026 is 31 days, because January has 31 days. 1 January 2026 to 1 January 2027 is 365 days, because 2026 is not a leap year. The result can also be read in weeks: 31 days is 4 weeks and 3 days, and 365 days is 52 weeks and 1 day.
- Adding days moves forward on the calendar. 1 November 2026 plus 30 days is 1 December 2026, because November has 30 days. 1 November 2026 plus 45 days is 16 December 2026, plus 90 days is 30 January 2027, and plus 180 days is 30 April 2027.
- Subtracting days moves backwards the same way. 1 November 2026 minus 30 days is 2 October 2026, because October has 31 days and 1 November minus 1 day is 31 October.
- Leap years add one day to February. 2028 is a leap year, so 28 February 2028 plus 1 day is 29 February 2028. 2027 is not a leap year, so 28 February 2027 plus 1 day is 1 March 2027.
Counting in whole calendar days also protects against daylight-saving time. Some days are 23 or 25 hours long where clocks change, and a calculator that divided hours by 24 would be a day out. This one counts dates, not hours, so a day is always a day.
Worked examples
Example 1 — days between 1 January 2026 and 1 February 2026. January has 31 days, so 1 February minus 1 January is 31 days — 4 weeks and 3 days. The same pair a year apart, 1 January 2026 to 1 January 2027, is 365 days — 52 weeks and 1 day — because 2026 has 365 days.
Example 2 — 30 days from 1 November 2026. November has 30 days, so adding 30 days to 1 November lands on 1 December 2026. Adding 45 days lands on 16 December 2026: 30 days takes you to 1 December, and 15 more days takes you to 16 December.
Example 3 — 90 and 180 days from 1 November 2026. Adding 90 days to 1 November 2026 gives 30 January 2027 — 30 days to 1 December, 31 more to 1 January 2027, and 29 more to 30 January. Adding 180 days gives 30 April 2027 — 61 days to 1 January 2027, then 31 days of January, 28 of February, 31 of March, and 29 days of April.
Example 4 — adding a full year. 1 January 2026 plus 365 days is 1 January 2027, because 2026 is not a leap year and has exactly 365 days. Adding 365 days to 1 January 2028 would land on 31 December 2028 instead, because 2028 is a leap year with 366 days — the extra day, 29 February 2028, falls inside the span.
Example 5 — leap years. 28 February 2028 plus 1 day is 29 February 2028, a date that only exists in leap years. 28 February 2027 plus 1 day is 1 March 2027, because February 2027 has only 28 days. The calculator knows which years are leap years, so you never have to work it out yourself.
Common mistakes
- Counting the end date twice. The most common error is adding one day too many: 1 January to 2 January is 1 day, not 2. This calculator counts end date minus start date, so the end date itself is not added on top. If you need the inclusive count — both dates counted — add 1 to the result.
- Forgetting the month lengths. “One month from 1 November” is 1 December, but “30 days from 1 November” is also 1 December, while “30 days from 1 January” is 31 January — because January has 31 days and November has 30. Days and months are different units, and a date calculator counts days.
- Assuming every year has 365 days. A year that contains 29 February has 366 days, so adding 365 days across a leap day lands one day short of the same date next year. 1 January 2028 plus 365 days is 31 December 2028, not 1 January 2029.
- Mixing up the date order. Days between two dates is a signed count: the later date minus the earlier date. If you enter the dates the wrong way round, the answer comes out negative. The calculator shows the negative count and explains that the end date is earlier, so swap the two dates to get the positive number.
- Counting hours instead of days. Some calculators divide the hours between two moments by 24, which goes wrong around daylight-saving changes — a 23-hour day makes the count one day short. This calculator counts whole calendar dates, so clock changes never affect the answer.
Related tools
The date calculator sits in the Everyday group, and three companion tools cover the other everyday counting jobs.
- Percentage Calculator — work out percentages, percentage change and percentage of a number, the same kind of everyday arithmetic as counting days.
- Playback Speed Calculator — work out how long a video, podcast or audiobook takes at a faster speed, and how much time you save.
- Compound Interest Calculator — see how savings grow over time, where the number of days and years in the calculation matters just as much as the rate.
For all of ToolZana’s free tools, start at the ToolZana home page.
Tips for counting days
- Say the convention out loud. Before you count, decide whether the end date counts: “1 January to 2 January is 1 day” is the convention this calculator uses, and it matches most deadlines, bookings and countdowns. If your booking counts both days, add 1.
- Use weeks for long spans. A span of 90 days is easier to picture as 12 weeks and 6 days, and 180 days as 25 weeks and 5 days. The calculator shows both, so you can use whichever reads better.
- Check leap years for spans over a year. If your span crosses February, check whether it contains 29 February. A span from 1 January 2028 to 1 January 2029 is 366 days, not 365.
- Work backwards from a deadline. If something is due on 30 April 2027 and you need 90 days to prepare, subtract 90 days to find your start date — 30 January 2027 — instead of guessing. The subtract mode does this in one step.
- Use the “days from today” tab for quick checks. 30, 45, 90 and 180 days are the spans people ask about most — a month, six weeks, three months and six months — and the tab shows all four at once from today’s date.
The short version
The Date Calculator counts the days between two dates as end date minus start date — 1 January 2026 to 1 February 2026 is 31 days, and 1 January 2026 to 1 January 2027 is 365 days. Adding days moves forward on the calendar: 1 November 2026 plus 30 days is 1 December 2026, plus 45 days is 16 December 2026, plus 90 days is 30 January 2027, and plus 180 days is 30 April 2027. Subtracting days moves backwards the same way. Leap years are handled automatically — 28 February 2028 plus 1 day is 29 February 2028, while 28 February 2027 plus 1 day is 1 March 2027 — and because the calculator counts whole calendar days, daylight-saving changes can never shift the answer. The tool is free, runs entirely in your browser, and needs no sign-in.
Frequently Asked Questions
What is a date calculator?
A date calculator is a free tool that does calendar arithmetic for you. It counts the days between two dates, adds or subtracts days from any date, and works out what date it will be a set number of days from today — for example 30, 45, 90 or 180 days from today. You pick the dates from a calendar picker, and the answer appears straight away, with leap years handled automatically.
How do I count the days between two dates?
Pick the earlier date as the start date and the later date as the end date, and the calculator subtracts one from the other. 1 January 2026 to 1 February 2026 is 31 days, because January has 31 days, and 1 January 2026 to 1 January 2027 is 365 days, because 2026 is not a leap year. The result also shows the same span in weeks and days — 31 days is 4 weeks and 3 days, and 365 days is 52 weeks and 1 day.
How do I add days to a date?
Pick your start date, choose “Add days”, and enter how many days. 1 November 2026 plus 30 days is 1 December 2026, because November has 30 days. To count backwards instead, choose “Subtract days” — 1 November 2026 minus 30 days is 2 October 2026. The result shows the new date and the maths behind it, so you can check it at a glance.
What is 30 days from today?
30 days from today is today’s date plus 30 days on the calendar. As an example, 30 days from 1 November 2026 is 1 December 2026, because November has 30 days. The exact date depends on which day today is, so open the “Days from today” tab on the calculator — it uses your device’s current date and shows the resulting date for 30 days, along with 45, 90 and 180 days.
What is 45 days from today?
45 days from today is today’s date plus 45 days on the calendar. As an example, 45 days from 1 November 2026 is 16 December 2026: 30 days takes you to 1 December, and 15 more days takes you to 16 December. The exact date depends on which day today is, so open the “Days from today” tab on the calculator — it uses your device’s current date and shows the resulting date for 45 days, along with 30, 90 and 180 days.
What is 90 days from today?
90 days from today is today’s date plus 90 days on the calendar — roughly three months. As an example, 90 days from 1 November 2026 is 30 January 2027: 30 days to 1 December, 31 more to 1 January 2027, and 29 more to 30 January. The exact date depends on which day today is, so open the “Days from today” tab on the calculator — it uses your device’s current date and shows the resulting date for 90 days, along with 30, 45 and 180 days.
What is 180 days from today?
180 days from today is today’s date plus 180 days on the calendar — roughly six months. As an example, 180 days from 1 November 2026 is 30 April 2027: 61 days to 1 January 2027, then 31 days of January, 28 of February, 31 of March, and 29 days of April. The exact date depends on which day today is, so open the “Days from today” tab on the calculator — it uses your device’s current date and shows the resulting date for 180 days, along with 30, 45 and 90 days.
Does the calculator include the end date in the count?
No — the count is end date minus start date, so the end date itself is not added on top. 1 January to 2 January is 1 day, not 2, and 1 January 2026 to 1 February 2026 is 31 days, not 32. This is the convention most deadlines, bookings and countdowns use. If you need the inclusive count, where both the start and end dates are counted, add 1 to the result — 1 January to 2 January inclusive is 2 days.
How does the calculator handle leap years?
Leap years are handled automatically. A leap year has 366 days because February gains a 29th day, and the calculator knows which years are leap years. 28 February 2028 plus 1 day is 29 February 2028, because 2028 is a leap year, while 28 February 2027 plus 1 day is 1 March 2027, because 2027 is not. A span that crosses 29 February is one day longer than the same span in a non-leap year — 1 January 2028 to 1 January 2029 is 366 days.
What happens if the end date is before the start date?
The count comes out negative, and the calculator explains it instead of failing. If you enter 1 February 2026 as the start date and 1 January 2026 as the end date, the result is minus 31 days, with a note saying the end date is 31 days before the start date. Swap the two dates around to get the positive number — 1 January 2026 to 1 February 2026 is 31 days.
Why does another date calculator give a different answer?
Almost always because of the counting convention. Some calculators count end date minus start date, like this one, and some count both dates, which adds 1 to every answer — 1 January to 2 January is 1 day on one and 2 days on the other. A few calculators divide hours by 24, which goes wrong around daylight-saving changes, because some days are 23 or 25 hours long. This calculator counts whole calendar dates, so clock changes never affect it, and it states its convention plainly: end date minus start date.
Is the date calculator free?
Yes — the Date Calculator is completely free, with no sign-in and no limits. It runs entirely in your browser, so nothing you enter is uploaded anywhere, and you can use it as often as you like, for any dates, in any of its three modes.