Two questions cover almost every date problem: how far apart are these two dates, and what date is N days from here. This calculator answers both, in calendar days and business days, and tells you the weekday of the result so you are not planning a delivery for a Sunday.
How it is calculated
- Days between dates is the plain difference: from the 1st to the 31st of the same month is 30 days. Turn on "count the end date too" to get 31, the way you would count days of a holiday or days of a course.
- The calendar difference (years, months, days) counts whole months first, so the 31st to the 28th of February is 28 days, not one month.
- Business days count Monday to Friday and ignore public holidays, which differ by country. Subtract any holidays in your range yourself.
- Adding months keeps the day of the month where possible: January 31 plus one month is February 28 (or 29), the last day of the shorter month, not March 3.
- Adding business days skips weekends: Friday plus one business day is Monday.
Examples
From March 1, 2026 to June 1, 2026: 92 days, exactly 3 months, 13 weeks and 1 day, 65 business days. Ninety days after March 1, 2026 is May 30, a Saturday; 90 business days after it is July 3.
Common uses
Payment terms ("net 30"), notice periods, project deadlines, pregnancy weeks, visa and passport validity (many countries require six months left), returns windows, contract renewals, and how many days until an event. For counting back from a due date use the subtract mode. If the date you need is a baby’s due date, the due date calculator counts the 280 days from the last period for you.
Frequently asked questions
How do I count days between two dates?
Subtract the earlier date from the later one. The calculator handles month lengths and leap years for you and shows the answer in days, weeks and business days.
What is the formula to count days between two dates?
Days = end date − start date. In Excel or Google Sheets, with the start date in A2 and the end date in B2, =B2-A2 or =DAYS(B2,A2) gives the same number. Add 1 if both the first and the last day should count.
How many days are there between 1 April and 30 June inclusive?
91 days: 30 in April, 31 in May and 30 in June. Without counting the end date it is 90. The answer is the same every year, because February is not in the range.
Should I count the start day, the end day, or both?
It depends on the question. Nights in a hotel: neither end (check-in to check-out). Days of a trip or a course: both. Deadlines like "within 30 days" usually start counting the day after. Use the "count the end date too" switch for the inclusive version.
How are business days counted?
Monday through Friday. Public holidays are not excluded because they vary by country and region; subtract them from the result if they fall in your range.
What date is 90 days from today?
Choose "Add or subtract", enter 90 days, and the result shows the date and its weekday. Today’s date is filled in by default.
How to calculate days from date?
Add the number of days to the start date and do not count the start day itself: 30 days from September 14 is October 14. The table under the result lists 7 to 365 days after and before the start date you enter, with the weekday of each.
What date format is mm, dd, yyyy?
Month, day, year, the format used in the United States: 09/10/2026 is September 10. Most other countries write day, month, year, so the same digits mean 9 October there. The ISO 8601 format, 2026-09-10, reads the same everywhere. This calculator writes dates with the month as a word to avoid the mix-up.
What happens when I add a month to the 31st?
You get the last day of the next month, because it has no 31st. This is the convention used by banks and most software.
Read more
- How to count days between two dates, and whether to count the first dayThe formula for days between dates, when to add 1 for counting both ends, how deadlines like "within 30 days" are counted in the US and the UK, and a table of common cases from hotel stays to whole years.
- How to calculate age from a date of birthThe formula for age in years, months and days, worked through by hand, the cases where it trips people up (the 31st, February 29), the Excel formula and its known flaw, and how Korean age differs.
Sources
- ISO 8601 date and time format
- Microsoft Support: DAYS function
- Gregorian calendar leap year rules (US Naval Observatory)
By Calcelate Team. Formula from the sources above.
- 2026-10-14 · Formula and texts checked