What this calculator is for
Counting the days between two dates comes up constantly: checking how much of a 90-day visa window you’ve used, tracking a training plan before race day, or working out whether a filing deadline has passed. By hand it’s error-prone — months differ in length, February changes in leap years, and finger-counting on a calendar is the classic way to end up off by one.
The tool gives you four readings of the same gap: the total days, the breakdown in weeks and days, an approximation in months and years (using the average month of 30.44 days), and the business days from Monday to Friday.
How to use it
- Pick the start date in the first field.
- Pick the end date in the second. Order doesn’t matter — the tool shows the absolute difference.
- Read the total days on the dark card.
- Check the smaller cards for the weeks, months, years and business-day breakdowns.
How the count works
Both dates are anchored to local midnight and the difference is divided by 86,400,000, the milliseconds in a day. Because the result is rounded to a whole day, daylight-saving shifts never skew it. What you get is the number of nights between the dates — an exclusive count that leaves out the start date; add 1 if you need to include both end dates.
Business days are counted by walking the range one day at a time and keeping only Mondays through Fridays. Public holidays are not subtracted — deduct those yourself using your country’s calendar.
Worked example
Say your marathon is on November 1, 2026 and training starts on March 15, 2026. March 15 is day 74 of the year (31 days of January + 28 of February + 15), and November 1 is day 305 (January through October add up to 304 days, plus 1). The difference is 305 − 74 = 231 days, which is exactly 33 weeks (33 × 7 = 231) — convenient, since marathon plans are written in weeks. That’s about 7.6 months, and the range holds 165 business days before subtracting holidays such as Memorial Day (May 25) and Labor Day (September 7). July 4 falls on a Saturday in 2026, so it wouldn’t reduce the count anyway.
Handy reference
| Common period | Days | In weeks and days |
|---|---|---|
| Two weeks | 14 | 2 weeks exactly |
| 30-day notice | 30 | 4 weeks and 2 days |
| 90-day visa window | 90 | 12 weeks and 6 days |
| Half a year | 182 or 183 | about 26 weeks |
| Common year | 365 | 52 weeks and 1 day |
| Leap year | 366 | 52 weeks and 2 days |
Frequently asked questions
How do I count business days around holidays?
Get the business-day figure from the tool, then subtract any public holiday that lands on a Monday through Friday inside your range. Watch out for observed dates: in the US, a Saturday holiday is often observed the Friday before, and a Sunday one the Monday after — the observed date is what removes a working day.
How many days does each month have?
Use the knuckle rule: make a fist and name the months across knuckles and valleys, starting with January. Knuckle months have 31 days; valley months 30, except February with 28 or 29. When you run out of knuckles, start over — that’s why July and August, on back-to-back knuckles, both have 31.
What is a leap year?
A year is a leap year if it’s divisible by 4, unless it’s divisible by 100 and not by 400. So 2024 was a leap year and 2028 will be; 2026 is not; 1900 was not, while 2000 was. In a leap year February has 29 days and the year has 366.
Does the result include both end dates?
No. The tool counts the nights between the dates, so the start date is excluded. Friday to Monday shows 3 days; counted inclusively it would be 4. If your deadline rules say “including the first day,” add 1.