Days Between Dates Calculator guide
Count exactly how many days separate two dates, plus the same span in weeks, in years-months-days, and in Monday-to-Friday workdays. Useful for deadlines, trips, contracts, and countdowns.
How the day count works
Every date is converted to a day number, the count of days since a fixed reference point, and the calculator subtracts one from the other. That is the same approach Excel uses with serial dates and databases use with Julian day numbers. It automatically accounts for months of different lengths and for February 29 in leap years.
The subtraction is done on calendar dates, not on clock times. That matters in the US: on the Sunday in March when clocks spring forward, a day is only 23 hours long. Code that divides milliseconds by 86,400,000 can report 0.96 of a day and round the wrong way. Counting whole calendar days avoids that bug entirely.
Inclusive or exclusive: the one-day question
The default result excludes the end date, which answers "how many days from A until B". From Monday to Friday is 4 days, the same way a clock goes from 9 to 5 in 8 hours. This is the standard for countdowns, interest accrual, shipping estimates, and age.
Tick "Include end date" when both the first and last day count, such as conference days, a vacation you want to count in days off, a medication course, or a 30-day challenge. A Monday-to-Friday event is 5 days inclusive. Most off-by-one arguments about dates come down to which of these two questions someone meant.
Worked examples
Holiday countdown: January 1, 2026 to December 25, 2026 is 358 days, or 51 weeks and 1 day. In years, months, and days it is 0y 11m 24d. Of those days, 256 are weekdays counting January 1 but not December 25; include the end date and it is 257.
Election countdown: March 1, 2026 to the November 3, 2026 midterm election is 247 days, 176 of them weekdays. If you are planning a campaign calendar around weekday volunteer shifts, the second number is the one that matters.
Leap years change answers. March 1, 2027 to March 1, 2028 is 365 days; March 1, 2028 to March 1, 2029 is also 365; but February 1, 2028 to March 1, 2028 is 29 days, because 2028 is a leap year.
Weekdays and business days
The Weekdays figure counts Monday through Friday. With the end date excluded, it counts the start date and every weekday up to but not including the end date. With the end date included, it matches Excel's NETWORKDAYS function, which counts both endpoints.
Holidays are not removed, because there is no single list. US federal employees get 11 paid holidays; many private employers give 8 to 10; stock markets close on 10 days a year, including Good Friday but not Veterans Day or Columbus Day. Subtract the holidays that apply to you from the weekday figure.
Common mistakes
Counting on your fingers across month ends. People forget that April, June, September, and November have 30 days, and that February changes. A span that looks like "about three months" can be anywhere from 89 to 92 days.
Using 30-day months for money. Some loans use a 30/360 day-count convention where every month counts as 30 days, while others use actual/365. If you are checking interest, find out which convention the contract uses before comparing numbers.
Mixing up "within 30 days" and "after 30 days". A deadline within 30 days of January 1 is January 31 at the latest; something that happens after 30 days happens on or after January 31. Read the wording, then decide whether to include the end date.
Related tools
To go from a start date and a number of days to a target date, use the date calculator. For a live countdown to a specific moment, down to the second, use the countdown timer. To find someone's exact age in years, months, and days, the age calculator uses the same calendar-date math.
Frequently asked questions
How many days are between two dates?
Subtract the earlier date from the later one in whole days. January 1 to December 25, 2026 is 358 days. The calculator does this for any pair of dates and handles leap years and daylight saving time automatically.
Should I include the end date?
It depends on the question. "How many days until" excludes it: Monday to Friday is 4 days. "How many days does the event last" includes it: a Monday-to-Friday conference is 5 days. Tick "Include end date" to add that one day.
How do I count business days between two dates?
Read the Weekdays (Mon-Fri) figure. January 1 to December 25, 2026 contains 256 weekdays counting the start but not the end, or 257 with the end date included, which matches Excel's NETWORKDAYS. Subtract any holidays that fall on weekdays.
How many days are in a year?
365, or 366 in a leap year. Leap years are divisible by 4, except century years not divisible by 400, so 2000 was a leap year and 2100 will not be. 2028 is the next leap year.
How many weeks are between two dates?
Divide the day count by 7. The calculator shows whole weeks plus leftover days, so 358 days reads as 51w 1d.
Does the order of the dates matter?
No. If the end date is earlier than the start date, the calculator swaps them and tells you, so the result is always a positive number of days.
Are my dates kept private?
Everything runs in your browser. Nothing you enter is uploaded to a server or stored by us.