Days Between Dates Calculator
Enter a start date and an end date to find out exactly how many days separate them. The calculator also shows the result in business days, weeks, months, years, hours, minutes, and seconds. Toggle whether to count the end date itself, see the day of the week for each date, and get a full breakdown panel showing every step of the math.
How to use this calculator
Enter a start date and an end date using the date pickers. The total day count updates immediately. Toggle "Count the end date itself" on if you want inclusive counting: for example, from Monday to Friday with the toggle on gives 5 days (Monday, Tuesday, Wednesday, Thursday, Friday), while leaving it off gives 4 (the number of full days that pass). You also get the result in business days, weeks, months, years, hours, minutes, and seconds, plus the day of the week for each date and a calendar breakdown in years, months, and remaining days.
How days between dates are calculated
The formula is straightforward: convert both dates to the number of milliseconds since a common epoch (1 January 1970 in most programming environments), subtract the earlier from the later, and divide by 86,400,000 (the number of milliseconds in one day). The result is the number of full days between the two dates, not counting the end day unless you choose the inclusive option. Business days are then counted by walking through the range one day at a time and skipping Saturdays and Sundays. The calendar breakdown (years, months, days) is computed separately using calendar arithmetic: whole years are subtracted first, then whole months, and whatever is left over becomes the remainder days.
Exclusive vs. inclusive counting
Which counting method is correct depends on what you are measuring. Exclusive counting (the default) answers the question "how many days pass between these two dates?" For example, there are 6 days between 1 January and 7 January. Inclusive counting answers "how many days are covered by this range, including both endpoints?" The same range covers 7 days: the 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th. Legal deadlines often use inclusive counting, while elapsed time (age, runtime, interest periods) uses exclusive counting. If you are unsure which to use, read the relevant contract, statute, or policy to see whether the start and end dates are themselves included.
Business days vs. calendar days
Calendar days count every day in the range: Mondays through Sundays, public holidays included. Business days count only weekdays: Monday, Tuesday, Wednesday, Thursday, and Friday. This calculator counts business days by the weekday definition only, without adjusting for public holidays, because holidays vary by country, region, and employer. If your deadline or contract specifies business days and names specific holidays as excluded, subtract those manually after using this calculator.
Common date spans as reference
| Period | Days (approx.) |
|---|---|
| 1 week | 7 |
| 2 weeks | 14 |
| 1 month | 30 |
| 1 quarter | 91 |
| 6 months | 182 |
| 1 year | 365 |
| 1 leap year | 366 |
| 2 years | 730 |
| 5 years | 1826 |
| 10 years | 3652 |
Approximate day counts for frequently used time periods.
Frequently asked questions
How many days between two dates?
To find the number of days between two dates, subtract the earlier date from the later date. In practice, that means converting each date to a numeric day count (or millisecond timestamp) and dividing the difference by 86,400,000 ms per day. This calculator does that instantly for any two dates you enter.
Does the calculator count the start date or the end date?
By default, the calculator uses exclusive counting: it does not count either endpoint as a full day of the span. This gives the number of complete days that pass between the two dates. If you want to count the end date itself (inclusive), toggle the "Count the end date itself" switch, which adds 1 to the result. The start date is never counted as an extra day.
How do I calculate business days between two dates?
Business days are weekdays only: Monday through Friday. This calculator counts them automatically alongside the calendar day total. Note that public holidays are not subtracted automatically because they differ by country and employer. If your calculation requires excluding specific holidays, use the total calendar result and subtract the number of holidays that fall on weekdays within the range.
What is the difference between calendar months and 30-day months?
A calendar month follows the actual calendar: January has 31 days, February has 28 or 29, and so on. When you ask "how many months between two dates?", the answer using calendar months is the count of full month boundaries crossed, which this calculator shows as part of the years-months-days breakdown. If you instead divide total days by 30 you get an approximation that ignores the varying month lengths.
Why might two methods give different month counts?
The calendar breakdown method (years, months, days) and the simple "divide by 30.44" method often give different results for the same date pair. That is because calendar months are unequal in length. For example, from 31 January to 28 February is exactly 1 calendar month, but it is only 28 days, whereas from 1 January to 31 January is also 30 days. If your use case demands precision, state which definition of "month" you are using.
Can I use this for a date in the past or future?
Yes. The calculator works for any two dates, past or future. If you put the later date in the start field and the earlier date in the end field, the calculator automatically swaps them and returns a positive result. Historical dates and dates centuries into the future are all supported.