Days between dates:
count the exact days from one date to another

How to count the days between two dates

The number of days between two dates is the later date minus the earlier date, counted in whole days. From 10 October 2026 to 9 November 2026 is 30 days. The day you start on is day zero, and the day you finish on is the last one counted.

People get different answers because they have counted differently, not because the arithmetic is hard. Before you start, settle whether the first day is counted, whether the last day is counted, and what happens when the dates cross a leap day.

The simplest reliable approach is to convert each date to its position in the year, subtract, and add the full years in between.

Two quick sanity checks help. Dates exactly one week apart are always 7 days apart, and the same date one year later is 365 days on, or 366 if a 29 February sits in between. If your answer breaks either rule, recount.

Days between dates formula

1. 1Find the day number of each date using the table below.
2. 2If both dates fall in the same year, subtract the smaller number from the larger.
3. 3If they fall in different years, add the days left in the first year, the full years in between and the day number in the last year.
4. 4Add 1 if the rule is to count both the start and the end date.

Day number reference table

Use this table to find a date's position in a non-leap year: take the cumulative total of the previous month and add the day of the month. In a leap year, add 1 for any date from 1 March onwards.

To find 15 November, take 304 at the end of October and add 15 to get day 319. To find 20 January, it is simply day 20.

Example: 20 January to 15 November 2026

To express 299 days in weeks, divide by 7: 42 weeks and 5 days, since 42 × 7 = 294. The weeks between dates calculator on this page does that conversion directly.

A second route confirms it. From 20 January to 20 October is 293 − 20 = 273 days, since 20 October is day 293. From 20 October to 15 November is 11 days to the end of October plus 15, which is 26. Adding 273 + 26 gives the same 299.

When you need a number for planning, such as the days of a project that runs through both end dates, use 300. When you need the elapsed gap, as with an interest period, use 299. Say which one you mean.

Counting across a leap day

A leap year has 366 days because February has 29. A year is a leap year when it divides by 4, except for century years, which must divide by 400. So 2024 and 2000 are leap years, while 2100 is not.

Nearby leap years are 2024 and 2028. The years 2025, 2026 and 2027 all have 365 days, and the next century exception arrives in 2100.

If you ignore leap years, a multi-year count will be a day or more short. For a loan or a lease running over several years, those days matter, so use actual dates rather than multiplying years by 365.

Countdowns and deadlines

From the other direction, the same arithmetic tells you the date a given number of days away. A 30-day notice served on 10 October 2026 ends on 9 November 2026, a Monday, when you do not count the day it was served.

• Days left in 2026 after 10 October: 82, to 31 December, or 83 days to 1 January 2027.
• Days from 10 October to Friday, 25 December 2026: 76.
• 90 days after 10 October 2026: Friday, 8 January 2027.

Refund and complaint windows work the same way. A rule that gives you 14 days from 10 October 2026 ends on 24 October, which is a Saturday. If the last day falls on a weekend or holiday, check whether the rule moves it to the next working day or not.

To go straight to the date that is a certain number of days away, the add days to a date calculator on this page does that. To drop weekends and holidays from the count, the business days guide shows the next step.

Mistakes that make the count wrong

• Counting both end dates by habit. A gap of 'one day' between 1 and 2 October counts only one day, not two.
• Using 30 days for every month. Months run from 28 to 31 days, so a flat 30 drifts away over a year.
• Forgetting the leap day. A range that includes 29 February has one more day than the same range in a non-leap year.
• Reading the date in the wrong order. 05/06/2026 is 5 June in India and 6 May in the US format, which is 30 days apart.
• Using a time of day as well as a date. A start at 11 pm and an end at 1 am the next day is 2 hours, not a day.

When two sources disagree by a day, do not average them. Rebuild each count from the same two dates using the same rule and the difference usually shows up straight away.