Date Calculator: Days Between Dates, Business Days, Countdown, Week Number
Days between two dates, business days, days until a date, and the ISO and US week number.
Inputs
- Total days
- 972
- Counting both the start and end day
- 973
- Weeks + days
- 138 weeks, 6 days
- Total months
- 31 months and 29 days
- From
- Monday, January 1, 2024
- To
- Sunday, August 30, 2026
Use this calculator on your own site
Free embed
- Two lines of HTML, unlimited views
- Shows a small CalculateEveryday bar, with a credit link under the calculator
What each Date input means
- Work out
- Which question to answer. The date boxes change with it; the two 'between' questions share the same start and end dates, so you can switch between calendar days and business days without retyping.
- Holidays
- For business days only: weekends alone, or weekends plus the US federal holidays on their observed days. Company days off are not known to the page; subtract them yourself.
- From date (optional)
- For the countdown, the day to count from. It starts as today, so the count changes by itself each day; set it to a booking date to see how far away the target was then.
- Date
- For the week number, any date. The answer gives the ISO week and its Monday-to-Sunday dates, the ISO week-year, and the US week number.
Date formula
days between = midnights from the first date to the second · calendar span = years, months, days with a month borrowed when needed · business days = weekdays in the span, both ends included, less observed holidays · ISO week = the Monday-start week, week 1 holding the year's first Thursday
Four questions about dates, one at a time. Days between two dates gives two honest answers: the calendar span in whole years, months and leftover days — borrowing the length of the month when the end day is smaller than the start day, as you would on a wall calendar — and the flat count of midnights from one date to the other, which is what interest, notice periods and countdowns use. A line below adds one for counts that include both ends, such as a hotel stay 'from and including'. Business days checks every day in the span, both ends included: Monday to Friday counts and the weekend does not, and the US option also takes out the eleven federal holidays on the day they are observed. Days until a date counts from today, or any day you set, to the target, so the day before reads 1 and the day itself 0; a past target reads as days ago. Week number gives both systems in use, because they disagree for part of every year. Leap years need no special handling, since every count walks the real calendar.
Date worked example
From 1 January 2024 to 30 August 2026 is 2 years, 7 months and 29 days. As a flat count it is 972 days — 2024 alone has 366 because it is a leap year — which is 138 weeks and 6 days, or 973 days if both the first and last day are counted.
More Date examples
All of 2026: 365 calendar days, less 104 weekend days, less the 11 federal holidays that land on weekdays, leaves 250 business days.
From Sunday 30 August 2026 to New Year's Day 2027 is 124 days — 17 weeks and 5 days, or 2,976 hours. On 31 December the countdown reads 1.
Friday 1 January 2027 is in ISO Week 53 of 2026, the week of Monday 28 December to Sunday 3 January, because 2026 started on a Thursday. In the US system the same day is week 1.
Where the Date calculator can give the wrong answer
- If the end date is before the start date, the dates are swapped and the difference shown, with a note.
- A month in the calendar answer is not a fixed number of days: 31 January to 28 February is 0 months and 28 days, while 1 February to 1 March is 1 month.
- Business days skip only US federal holidays. State holidays, bank holidays outside the federal list and company days off still count.
- The countdown is in whole days and ignores the time of day: at 11 pm the night before, it still says 1. Sites that count today as day 1 show one more.
- Early January can fall in ISO week 52 or 53 of the previous year, and late December in week 1 of the next. Read the ISO week-year line.
- Times of day are ignored throughout. Use the hours calculator for a span inside one day.
Spotted a mistake? Tell us
Date reference table
| Holiday | 2026 | 2027 |
|---|---|---|
| New Year's Day | Thu 1 Jan | Fri 1 Jan |
| Martin Luther King Jr. Day | Mon 19 Jan | Mon 18 Jan |
| Washington's Birthday | Mon 16 Feb | Mon 15 Feb |
| Memorial Day | Mon 25 May | Mon 31 May |
| Juneteenth | Fri 19 Jun | Fri 18 Jun (19th is a Saturday) |
| Independence Day | Fri 3 Jul (4th is a Saturday) | Mon 5 Jul (4th is a Sunday) |
| Labor Day | Mon 7 Sep | Mon 6 Sep |
| Columbus Day | Mon 12 Oct | Mon 11 Oct |
| Veterans Day | Wed 11 Nov | Thu 11 Nov |
| Thanksgiving | Thu 26 Nov | Thu 25 Nov |
| Christmas | Fri 25 Dec | Fri 24 Dec (25th is a Saturday) |
Date FAQ
- Choose 'Days between two dates' and enter both. The 'Total days' line counts from the first midnight to the second: 1 January to 31 December in the same year is 364, or 365 counting both days.
- The total counts the days crossed, so 1 January to 2 January is 1 day, and a line adds one for inclusive counts. Business days are different: both ends count when they are weekdays.
- The calendar answer counts whole months plus the days left over — 2 years 7 months is 31 months. In Excel, =DATEDIF(start, end, "m") gives the same whole months.
- 261 weekdays, or 250 after the eleven US federal holidays, with Independence Day (a Saturday) observed on Friday 3 July.
- A Saturday holiday is observed the Friday before and a Sunday holiday the Monday after, per OPM. The page skips the observed day, so New Year's Day 2028 comes off Friday 31 December 2027.
- Between 20 and 23 weekdays before holidays. A common-year February has exactly 20; a 31-day month has 21 to 23, depending on the weekday it starts on.
- Choose 'Days until a date' and set 25 December. From 22 October 2026 it is 64 days — 9 weeks and 1 day, or 64 sleeps.
- No. It counts the days still to come, so the day before the event shows 1 and the event itself 0.
- Choose 'Week number of a date' and enter today. The page shows the ISO number used in Europe and the US Sunday-start number, which can differ by one.
- ISO weeks start on Monday and week 1 holds the year's first Thursday; US weeks start on Sunday and week 1 holds 1 January. 30 August 2026 is ISO week 35 but US week 36.
- 52 or 53. In ISO numbering 2026 has 53 weeks, because it starts on a Thursday, so 1 January 2027 is in week 53 of 2026.
- WEEKNUM's default is the US system. ISOWEEKNUM, or WEEKNUM with return type 21, gives the ISO week.
- 365, or 366 in a leap year. A year is a leap year when it divides by 4, except century years, which must divide by 400 — 2000 was one and 2100 will not be.