How to calculate the days between two dates
Utilio editorial teamPublished: 6 min read
To count the days between two dates, add the days left in the first month, the days of every full month in between and the days that have passed in the last month. From October 10 to December 25, 2026 there are 21 + 30 + 25 = 76 days. What changes the answer isn’t the addition but two decisions you make first: whether the last day counts, and whether only business days count.
The by-hand method, step by step
From October 10 to December 25, 2026
Days left in October after the 10th: 31 − 10 = 21.
All of November: 30 days.
Days of December up to the 25th: 25.
21 + 30 + 25 = 76 days
You need to know how many days each month has: 31 for January, March, May, July, August, October and December; 30 for April, June, September and November; and 28 for February, or 29 in leap years (2024 and 2028, for example).
Should the last day count?
The method above measures the gap between dates: Monday to Tuesday is 1 day. But sometimes both ends count:
| Situation | August 1 to August 7 | Why |
|---|---|---|
| Time elapsed | 6 days | You measure the distance between the dates |
| Length of a trip or leave | 7 days | Every occupied day counts, including the first and the last |
| Hotel nights | 6 nights | You pay for each night between check-in and check-out |
Counting both ends
Days = (end date − start date) + 1
Pick two dates and get the days, weeks, months and business days, with or without the last day.
Open the date calculatorCalendar days and business days
Calendar days are every day on the calendar. Business days exclude weekends and, usually, public holidays. To count Monday-to-Friday days without walking through the calendar, group by full weeks: each week has 5 business days.
Monday, October 5 to Friday, October 30, 2026, both included
That’s 26 days in total: 3 full weeks (15 weekdays) plus 5 extra days, Monday 26 to Friday 30 (5 weekdays).
Monday, October 12, 2026 is Columbus Day / Indigenous Peoples’ Day, a federal holiday. If your employer or bank observes it, there are 19 business days.
20 weekdays
Legal deadlines follow their own counting rules. For example, in US federal civil cases, Rule 6(a) of the Federal Rules of Civil Procedure excludes the day of the triggering event, counts every following day including weekends and holidays, and moves a deadline that falls on a weekend or legal holiday to the next day that isn’t one. State courts and agencies can use different rules, so always check the ones for your case.
30 days isn’t the same as one month
A “one month” period ends on the same day of the next month, while a “30 days” period is counted day by day:
| From January 15, 2026 | Result |
|---|---|
| + 30 days | February 14 |
| + 1 month | February 15 |
And when the day doesn’t exist in the target month, the last day of the month is used: January 31 plus one month is February 28.
How to do it in Excel or Google Sheets
- Days between two dates: subtract the cells,
=B1-A1, and format the result as a number. To count the last day too, use=B1-A1+1. - Business days:
=NETWORKDAYS(A1,B1)counts Monday-to-Friday days including both dates. Add a range of holidays as a third argument:=NETWORKDAYS(A1,B1,F1:F10). - Adding business days to a date:
=WORKDAY(A1,10)returns the date 10 business days later.
Frequently asked questions
How many days are in a year?
365, or 366 in leap years. A year is a leap year if it’s divisible by 4, except years divisible by 100 that aren’t divisible by 400.
How many weeks are there between two dates?
Divide the days by 7. For example, 76 days is 10 full weeks and 6 days.
What date is 90 days from now?
Add the days month by month, or use the date calculator’s “Add or subtract” mode. From October 10, 2026, 90 days later is January 8, 2027.
Tools in this guide
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