Days between two dates calculator
Pick a start date and an end date to get the exact number of days between them, the same span as weeks and days and as calendar months and days, and the weekday of each date. Choose whether the end day counts. The arithmetic runs in your browser, so it works offline and there is nothing to sign up for.
How to use it
Enter the two dates in any order; the calculator measures from the earlier one to the later one. Leave 'include end day' off for the plain difference, which is what most people mean by 'how many days between'. Switch it on when both the first and the last day count, such as the days a rental runs or a billing period. The result shows days, weeks and days, months and days, and the weekday of each date, so you can check it against a wall calendar.
If one date is in the past, the same tool works as a 'days since' counter. For a live number that keeps ticking down to a future date, use the custom countdown page instead; this page is for one-off arithmetic.
Include the end day or not? The formula
Two dates can be a different number of days apart depending on what you are counting, and this is the most common reason two people get two answers. The exclusive count is end minus start: Monday to Friday is 4 days. The inclusive count adds one because it counts the days themselves rather than the gaps between them: Monday through Friday is 5 days. This calculator shows the exclusive count by default and adds 1 when 'include end day' is on. Ages, deadlines and countdowns are exclusive. Hotel nights are exclusive (in Friday, out Sunday: 2 nights) while the days you were away are inclusive (3 days).
Contracts and laws usually say which applies. In most US and UK legal drafting the day an event happens is excluded and the last day is included, so a 30-day notice given on March 1 expires at the end of March 31. Korea's Civil Act Article 157 uses the same first-day-excluded rule. Korean couples count the other way: the first day together is day 1, so a 100th-day anniversary is 99 days after the start date.
Weeks and months: how the conversion works
Weeks are exact: the day count is divided by 7 and the remainder shown as days, so 112 days is '16 weeks and 0 days' and 100 days is '14 weeks and 2 days'. Months are not exact because they run 28 to 31 days. The calendar method used here steps forward whole months to the same day-of-month and then counts leftover days: September 4 to December 25 is 3 months (to December 4) and 21 days. When the start day-of-month does not exist in a later month it clamps to the last day, so January 31 plus one month is February 28 or 29.
The other method treats a month as an average 30.44 days (365.25 ÷ 12) and gives decimals like '3.68 months'; it suits interest and pro-rata sums but not dates, so it is not used here. Leap years are handled automatically: February 29, 2028 is a real day in the count, and March 1, 2027 to March 1, 2028 is 366 days because it contains that leap day.
Worked examples
Spans you can check the tool against. Each row gives the exclusive count first and the inclusive count in brackets.
| From → to | Days (incl.) | Weeks / months |
|---|---|---|
| Jan 1, 2026 → Dec 31, 2026 | 364 (365) | 52 weeks 0 days / 11 months 30 days |
| Sep 4, 2026 → Dec 25, 2026 | 112 (113) | 16 weeks 0 days / 3 months 21 days |
| Feb 14, 2026 → Feb 14, 2027 | 365 (366) | 52 weeks 1 day / 12 months 0 days |
| Jan 1, 2028 → Jan 1, 2029 (leap year) | 366 (367) | 52 weeks 2 days / 12 months 0 days |
| Jan 1, 2026 → Apr 10, 2026 (100th day) | 99 (100) | 14 weeks 1 day / 3 months 9 days |
| Jan 1, 2026 → Sep 4, 2026 (days since) | 246 (247) | 35 weeks 1 day / 8 months 3 days |
Where people use this
Pregnancy due dates are 280 days, or 40 weeks, after the first day of the last period, which is why obstetricians talk in weeks and days. Visa rules such as the Schengen 90-in-180 limit count arrival and departure days as full days. Freelancers price projects from working days rather than calendar days; the working days calculator on this site does that. In Korea the same arithmetic covers the college entrance exam D-day (November 19, 2026), 100-day anniversaries and notice periods under the first-day-excluded rule.
What this calculator does not do
It works in whole calendar days and ignores time of day and time zones, so a flight leaving at 11 pm and landing at 1 am is one day apart. It applies the modern Gregorian calendar to every year, so dates before 1582 will not match historical records. It knows nothing about weekends or holidays; the working days calculator adds those. And it counts days, not nights, so a hotel quote will be one lower than the inclusive figure shown.
Frequently asked questions
- How many days are between two dates?
- Subtract the earlier date from the later one. The calculator does this in whole calendar days and adds one if 'include end day' is on.
- Should I include the end date?
- Include it when counting the days themselves (days of a trip, billing days, shopping days). Exclude it when measuring a gap (age, time to a deadline, nights).
- How do I count days since a past date?
- Put the past date in one field and today in the other. Add one if the first day should count as day 1, as in a streak or anniversary.
- Why does the months figure look odd?
- Months differ in length, so the tool steps whole calendar months to the same day-of-month and reports the remainder as days, clamping January 31 to the end of February.
- Does it handle leap years?
- Yes. February 29 is counted whenever it falls inside the span; 2028 and 2032 are the next leap years.
- Is my data stored anywhere?
- No. The dates never leave your browser; there is no account, no upload and no limit on calculations.
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