Calendar math, made clear
Date Difference Calculator — Free Online
✓ 100% FREE — No Signup Needed
Use this free online date difference calculator to count the exact days between any two dates — or see how many days have passed since a date. No signup needed; totals for days, weeks, months, years and weekdays included.
Elapsed time excludes the start date. For example, Monday to Tuesday is one day.
Quick answer: How do I calculate the days between two dates manually? Count the days left in your start month, add the full days of every whole month between them, then add the end date's day number. Example: 20 October to 15 December 2026 is 11 days left in October + 30 in November + 15 in December = 56 days.
Please choose both a start date and an end date.
Exact calendar duration
0 days
Dates were entered in reverse order, so the absolute difference is shown.
How the date count works
The result uses calendar dates rather than clock time, so daylight-saving changes do not alter the answer.
- Select two datesPick the beginning and end of your trip, project, age range, or countdown.
- Read the exact durationCalendar years and months are counted first, followed by the remaining days.
- Compare useful totalsSee elapsed days and weeks, plus average-length month and year estimates.
How do I calculate the days between two dates manually
You don't need a calculator — just three numbers. Here's the simple way to do it by hand:
- Count the days left in your start month. Take the month's total days and subtract the start day number. October has 31 days, so starting on 20 October leaves 31 − 20 = 11 days.
- Add every full month in between. November has 30 days — that's 30 straight.
- Add the end month's day number. Ending on 15 December adds 15 days.
- Add them together. 11 + 30 + 15 = 56 days from 20 October to 15 December.
Watch out for February (28 days, or 29 in a leap year) and remember that July and August both have 31 days. Prefer instant answers? Enter the two dates in the calculator above and it does this arithmetic for you, leap years included.
Helpful details
Frequently asked questions
How do I calculate the days between two dates manually without a calendar?
How do I calculate the days between two dates manually without a calendar? You need to know the number of days in each month by heart: 31 for January, March, May, July, August, October and December; 30 for the rest except February. Then add the days left in the start month, the full months between, and the end month's days — the free calculator above double-checks your answer.
How do I calculate the days between two dates manually across leap years?
How do I calculate the days between two dates manually across leap years? Use the same three-part method, but count February as 29 days when your range passes through a leap year (any year divisible by 4, except century years not divisible by 400). The calculator above handles this automatically.
How do I calculate days between two dates?
Select a start date and an end date above. The calculator subtracts the earlier date from the later date and displays the elapsed number of days instantly.
Does the calculation include the start date?
No. It measures elapsed time, so the start date is excluded. The same date returns zero days, while two consecutive dates return one day.
Why are total months and years marked with an asterisk?
Months have different lengths, and leap years have an extra day. Those two totals are estimates based on the average Gregorian month (30.436875 days) and year (365.2425 days). The exact calendar duration above them uses real calendar boundaries.
Are leap years included?
Yes. The total day count uses actual calendar dates, including February 29 when it occurs.
How many days have passed since a date?
Set the start date to that date and leave the end date on today. The calculator shows exactly how many days have passed, using real calendar dates with leap years included. It also works for counting days since birthdays, anniversaries, or the day you quit a habit.
Content last updated: October 2026.