Calculators

Date Calculator

Calculate the number of days and weeks between two dates, or add and subtract days from a date to find a future or past date.

Calculators · Date CalculatorRuns in your browser

Start date

End date

Include the end day in the total

How to count days between dates or add days to a date

Choose a mode with the toggle: Days between for the gap between two dates, or Add / subtract to move forwards or backwards from a date.
In Days between, pick a start date and an end date, and tick ‘Include the end day in the total’ if the last day should be counted.
In Add / subtract, pick a start date and type the number of days; a negative number goes back in time.
Read the result: the total days with a weeks-and-days breakdown, or the resulting date with its weekday.

How the day count is worked out

Both dates are taken at midnight, the difference in milliseconds is divided by 86,400,000 (the milliseconds in a day) and rounded to the nearest whole day. Because the dates are read as calendar dates rather than clock times, daylight-saving changes never add or remove an hour from the count.

From 1 January 2026 to 1 March 2026 the tool reports 59 days, shown alongside as 8w 3d (8 × 7 = 56, plus 3). From 19 October 2026 to 25 December 2026 it reports 67 days, or 9w 4d. Leap years are picked up automatically: 28 February to 1 March is 2 days in 2024 and 1 day in 2025.

The weeks figure is the total divided by 7 and rounded down, and the leftover is shown as days. There is no months or years breakdown on this page; the age calculator's Difference mode provides that.

When to tick ‘Include the end day’

Ticking the box adds exactly one day to the total. If the end date is earlier than the start date the total is negative, and the box makes it one day more negative, so −3 becomes −4.

Situation	Tick the box?	Example
Hotel nights	No	Friday 3rd to Monday 6th = 3 nights
Days of an event or holiday	Yes	3rd to 6th inclusive = 4 days
Deadline ‘within 30 days of’ a date	No	The notice day itself is not counted
Days since something happened	No	A straightforward elapsed count
Days of annual leave booked	Yes	First and last day are both taken

Adding and subtracting days

The Add / subtract mode shifts the start date by the number you type and shows the result with its weekday, in your browser's language and date format. 1 January 2026 plus 90 days is Wednesday 1 April 2026. 31 January 2026 plus 30 days is Monday 2 March 2026, because February 2026 has 28 days. 19 October 2026 minus 45 days is Friday 4 September 2026.

Only days can be added. For weeks, multiply by 7 first (6 weeks = 42 days). Adding months is a different operation, because months vary in length, and is handled by the separate add-days and subtract-days pages.

A time-zone quirk to know about

Both modes work on calendar dates, not on clock times, so your time zone does not change the answer. The Days between mode compares the two dates at midnight and divides by 86,400 seconds, rounding away any daylight-saving hour; the Add / subtract mode shifts the start date one calendar day at a time, so crossing a clock change or a month boundary never gains or loses a day. A quick sanity check: type 0 in the days field and the result should be exactly your start date.

What this page does not do

It counts every calendar day, including weekends and public holidays. Use the business days calculator for working days.
It ignores the time of day; a date is a date.
It shows no months or years, only days and weeks.
Both modes keep their own inputs, so you can switch back and forth without losing what you typed.
A half-entered date, or an empty days field in Add / subtract mode, simply shows no result rather than an error.

Frequently asked questions

Does this count both the start and end date?

The difference is the number of full days between the two dates. You can toggle whether the end day is included.

Why is my result negative?

The end date is earlier than the start date. Swap the two dates if you want a positive count; the size of the number is the same either way.

How do I add weeks or months instead of days?

For weeks, type the number of weeks multiplied by 7, so 8 weeks is 56 days. Months are not a fixed number of days, so use the dedicated add-days or subtract-days pages, which offer a months unit.

Can I find the date 100 days from today?

Yes. Switch to Add / subtract, pick today's date in the start field and type 100. The resulting date appears with its day of the week.

Does the count include weekends and holidays?

Yes, it counts every calendar day. For a count that skips Saturdays, Sundays and public holidays, use the business days calculator.

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