How the days are counted
By default, the calculator counts the number of days you move forward on the calendar to get from the start date to the end date. From Monday to Wednesday is 2 days: Monday to Tuesday, then Tuesday to Wednesday. This is how most people count "days until" something.
Tick include the end date when both the first and last days count, like a hotel booking from the 1st to the 5th where you want to know how many calendar dates are covered, or a 14-day leave period that starts and ends on working days. Including the end date adds one day.
Weekdays and business days
The weekday count includes Monday through Friday and skips Saturdays and Sundays. It counts from the start date up to, but not including, the end date (or including it, if you ticked the box).
It doesn't know about public holidays, because those differ by country and region. To get working days, subtract any holidays that fall on weekdays in your range.
Example: a contract says payment is due 30 working days after the invoice date. Find a date roughly 6 weeks later, check that the weekday count is 30, then subtract holidays and move forward by that many weekdays.
Counting days by hand
For short ranges, count the days left in the start month, add the full months in between, then add the days into the end month.
From 20 March to 15 June (same year):
Rest of March: 31 − 20 = 11. April: 30. May: 31. June: 15.
11 + 30 + 31 + 15 = 87 days.
Remember month lengths with the knuckle trick: make a fist, and count months across your knuckles and the dips between them. Knuckle months (Jan, Mar, May, Jul, Aug, Oct, Dec) have 31 days. Dip months have 30, except February, which has 28 or 29.
Common uses
- Countdowns: days until a wedding, exam, holiday or due date.
- Notice periods and deadlines: how many days you have left to respond, return an item or file a claim.
- Travel and visas: length of stay, since many visas limit days in a period. Check whether your authority counts arrival and departure days. Many do, which means including the end date.
- Interest and billing: some loans and bills charge per day, so the exact day count matters.
- Pregnancy: due dates are about 280 days (40 weeks) from the first day of the last period.
Frequently asked questions
Does daylight saving time affect the count?
No. The calculator works with whole calendar dates, so clock changes never add or remove a day.
What if the end date is before the start date?
The dates are swapped automatically and you'll get the positive number of days between them.
How many days are in a year?
365 in a normal year and 366 in a leap year. The calculator handles leap years automatically.
How old is someone in days?
The age calculator shows age in years, months and days, plus the total days lived.
Last reviewed November 2026.