Date Difference Calculator
Pick a start date and an end date, and this date difference calculator tells you how many days are between them. You also get the gap in years, months and days, in weeks plus days, in total months, in hours, and the number of weekdays (Monday to Friday). Tick one box to count both the first and the last day.
Updated
Results
- Years
- MonthsIn addition to the years
- DaysIn addition to the years and months
- Full weeks
- Remaining daysAfter the full weeks
- Total full months
- Weekdays (Mon–Fri)Holidays not removed
- Total hoursDays × 24; negative if the end date is earlier
Results are estimates. See the methodology below.
How to use the calculator
- Start date: the first day of the period, such as a contract start or today's date.
- End date: the last day, such as a deadline or a holiday.
- Include the end date: leave it unchecked to get the plain difference (the usual "days until" count). Check it when both days belong to the period, for example a vacation from the 1st through the 10th, which is 10 days, not 9.
If the end date is earlier than the start date, total days and total hours come out negative and the years/months/days line starts with a minus sign, so you can tell how long ago something happened. Weeks, months and weekdays still show the size of the gap as positive numbers.
How the dates are counted
Dates are treated as whole calendar days on the Gregorian calendar, in the ISO 8601 year-month-day order (YYYY-MM-DD), with no time zones. That way daylight saving changes never add or remove an hour.
- Total days = end date − start date, plus 1 if you include the end date.
- Years / months / days uses the anniversary method: count how many monthly anniversaries of the start date fit before the end date, then the leftover days. When a month is too short (a start on the 31st, or February 29), the anniversary falls on that month's last day. This is the same rule our age calculator uses.
- Weeks and days = total days ÷ 7, with the remainder.
- Weekdays counts every Monday through Friday in the period. Federal and state holidays are not removed; for that, use our business days calculator.
- Hours = total days × 24, negative like the total when the dates are inverted.
Worked examples
1. Days until Christmas
From Monday, October 12, 2026 to Friday, December 25, 2026 there are 74 days: 2 months and 13 days, or 10 weeks and 4 days. That span has 54 weekdays. If you count both October 12 and December 25, you get 75 days.
2. A school year
From September 1, 2026 to June 30, 2027:
| Setting | Total days | Y / M / D | Weekdays |
|---|---|---|---|
| End date not included | 302 | 0 / 9 / 29 | 216 |
| End date included | 303 | 0 / 10 / 0 | 217 |
Including the last day turns 9 months and 29 days into exactly 10 months, because the period now runs through the end of June.
3. A lease that starts on the 31st
A six-month lease begins August 31, 2026. September has no 31st, so the first monthly anniversary is September 30: 30 days, counted as 1 month. Enter August 31, 2026 to February 28, 2027 and you get 181 days and exactly 6 months (0 / 6 / 0), because February's anniversary falls on its last day.
4. Looking back
From October 12, 2026 back to July 4, 2026, the 250th Independence Day, the calculator shows −100 days, −2,400 hours and −0 / 3 / 8, while the 14 weeks and 2 days and the 70 weekdays stay positive.
Reading the results and legal deadlines
A "month" can be 28 to 31 days long, so when a precise length matters, rely on total days.
For deadlines in federal civil cases, Rule 6(a) of the Federal Rules of Civil Procedure says to exclude the day of the triggering event, count every day including weekends and legal holidays, and include the last day; if that day is a Saturday, Sunday or legal holiday, the period runs to the next day that isn't. This calculator's default count matches the first three steps but does not move a deadline off a weekend or holiday. Other courts, agencies and contracts may follow different rules.
Frequently asked questions
Does the calculator count the start date?
By default it gives the difference between the dates, which is the same as counting every day after the start date up to and including the end date. Check "Include the end date" to count both endpoints, which adds one day.
How many days are there in a year?
365 in a common year and 366 in a leap year. On the Gregorian calendar, years divisible by 4 are leap years except century years not divisible by 400, so 2000 was a leap year and 2100 won't be. February 29, 2024 to February 28, 2028 spans 1,460 days (3 years, 11 months, 30 days); through February 29, 2028 it is 1,461 days, exactly 4 years.
Are holidays excluded from the weekday count?
No. The weekday figure removes only Saturdays and Sundays. For example, October 12 to December 25, 2026 has 54 weekdays, including Thanksgiving. Subtract holidays yourself or use our business days calculator.
What happens if I enter the dates in the wrong order?
The total days and total hours turn negative, and the years/months/days line gets a leading minus sign: from December 25 back to October 12, 2026 you see −74 days, −1,776 hours and −0 / 2 / 13. The weeks and weekdays show the size of the gap.
Why is the hour count a whole number of days times 24?
The calculator works with calendar dates, not clock times, and ignores daylight saving time. For hours between two specific times, use our time duration calculator.
Sources
This calculator counts calendar days for general planning. It is not legal advice; for court, tax or contract deadlines, follow the rules that govern your case.