How to Count Days Between Two Dates (Easy Methods)
Ask three people how many days there are between 1 March and 25 December and there's a good chance you'll get three different answers. Nobody's maths is wrong, exactly. They're just counting different things, and most of them haven't noticed.
Counting days sounds like the simplest sum there is. In practice it catches people out all the time: hotel bookings, notice periods, medication courses, "only 100 days to go" posts that turn out to be 99. So here's how to do it properly, whether you've got a pen, a phone or a spreadsheet open.
First, decide what you're actually counting
This is where nearly every disagreement starts. There are two common ways to count:
Days between two dates, which doesn't count the start day. From Monday to Wednesday is 2 days.
Days including both ends, which counts the first and last day. Monday to Wednesday is 3 days.
Neither is wrong. A countdown uses the first one: if the event is tomorrow, there's 1 day to go, not 2. A hotel works the same way, because Monday to Wednesday is two nights. But a festival that runs from Monday to Wednesday is a three-day festival, and a course of tablets taken from the 1st to the 10th is ten days of tablets.
So before you start, ask yourself one question: does the first day count? If you're counting down to something, it usually doesn't. If you're counting how long something lasts, it usually does, and you add 1 to the answer.
Counting by hand
Let's take 1 March to 25 December 2026, which is a decent test because it crosses most of the year.
The trick is to count the rest of the first month, then whole months, then the days into the final month.
March: 31 days in the month, and we're starting on the 1st, so 30 days remain.
April to November: 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 = 244 days.
December: 25 days.
Add them together and you get 30 + 244 + 25 = 299 days between the two dates. If you wanted to count both the 1st of March and Christmas Day itself, it would be 300.
If you can never remember which months have 31 days, there's the old knuckle trick. Make two fists and hold them side by side. Starting from the left, each knuckle is a 31-day month and each dip between knuckles is a shorter one. January lands on a knuckle, February in a dip, March on a knuckle, and so on. When you reach the last knuckle of your first hand (July), jump straight to the first knuckle of the second hand for August. That's why July and August both have 31 days.
The one exception you have to carry in your head is February, which has 28 days, or 29 in a leap year. If your count crosses the end of February, check the year. 2028 is the next leap year, so February 2028 has 29 days.
Counting in Excel or Google Sheets
If you're doing this more than once, a spreadsheet is faster and doesn't get tired.
In both Excel and Google Sheets, dates are stored as numbers, so you can simply subtract one from the other. Put the start date in cell A1 and the end date in B1, then type:
=B1-A1
You'll get the number of days between them, not counting the first day. If the cell shows a date instead of a number, change its format to "Number".
Google Sheets also has a dedicated function, which reads more clearly if someone else will look at your sheet:
=DAYS(B1, A1)
Note that the end date comes first. It's easy to get that the wrong way round and end up with a negative number.
For working days only, use =NETWORKDAYS(A1, B1). This one skips Saturdays and Sundays and, unlike plain subtraction, it counts both the start and end date if they're weekdays. You can add a third argument with a list of bank holidays so it skips those too. It's handy for notice periods and delivery estimates, where weekends don't count.
Counting on your phone
You don't need an app. Most phone calendars will tell you the gap if you create an event and look at the details, but the quickest route is usually a search engine: type "days between 1 March and 25 December" and you'll get the answer straight away.
Or, if the date is something lots of people are waiting for, there's a good chance a live countdown already exists. Our How long until page lists every countdown we track, from Christmas to film releases and elections, and does the counting for you to the second.
The mistakes that catch people out
A few things go wrong again and again.
Forgetting the leap day. Count from January to March in a leap year and you'll be a day short if you assume February has 28 days.
Mixing up "in 7 days" and "a week on Friday". Spoken dates are slippery. If it matters, write the actual date down.
Time zones. A day starts at different moments around the world. Something happening at midnight in London has already happened in Sydney and hasn't happened yet in New York. That's why every countdown on this site runs to a stated moment in UTC, so there's no confusion about which midnight we mean.
Counting sleeps. Children count down in sleeps, and they're right to. The number of sleeps until a date is exactly the number of days between, because you don't sleep on the last day before it arrives. "Ten sleeps until Christmas" means it's ten days away.
A quick way to check your answer
If you've done the sum by hand, sanity-check it. A full year is 365 days, so anything from early in the year to late in the year should come in just under that. Six months is roughly 182 days. A month is 28 to 31. If your answer for March to December is 400, something's gone wrong.
It's also worth checking the weekday. If you know the start date is a Sunday and your count is a multiple of 7, the end date should be a Sunday too. 299 isn't a multiple of 7, so 1 March and 25 December 2026 fall on different days of the week. (They do: a Sunday and a Friday.)