The calculator counts calendar days from the start date up to the end date. The start date counts and the end date doesn't, unless you tick "Include end date". This is the same convention used in contracts, finance and most date tools.
How to count days between two dates by hand
- Count the days left in the start month (days in the month minus the start day).
- Add the days in every full month in between (see the table below).
- Add the day number of the end date.
- Add 1 if you want to include both the start and end dates.
Example: March 10 to June 5. March has 31 − 10 = 21 days left. April (30) + May (31) = 61. Add June's 5 days: 21 + 61 + 5 = 87 days.
| Month | Days | Month | Days |
|---|---|---|---|
| January | 31 | July | 31 |
| February | 28 (29 in leap years) | August | 31 |
| March | 31 | September | 30 |
| April | 30 | October | 31 |
| May | 31 | November | 30 |
| June | 30 | December | 31 |
A quick rule: make fists and count the months across your knuckles. Every knuckle is a 31-day month, every dip is 30 (or February).
Include the end date or not?
| Situation | Include end date? | Example |
|---|---|---|
| "How many days until…" | No | Today to Christmas |
| Age or time elapsed | No | Days since a birthday |
| Hotel stay (nights) | No | Check-in Mon, check-out Fri = 4 nights |
| Length of an event, course or leave | Yes | Mon–Fri course = 5 days |
| Visa or permit day limits | Usually yes | Entry and exit days both count in many rules; check the official rule |
Business days and holidays
Business days are counted from Monday to Friday. With "Exclude US federal holidays" ticked, the calculator also skips the 11 federal holidays: New Year's Day, Martin Luther King Jr. Day, Presidents' Day, Memorial Day, Juneteenth, Independence Day, Labor Day, Columbus Day, Veterans Day, Thanksgiving and Christmas. When a holiday falls on a Saturday it's observed on the Friday before; when it falls on a Sunday, on the Monday after.
Common date questions
| Question | Answer |
|---|---|
| Days in a year | 365 (366 in a leap year) |
| Weeks in a year | 52 weeks and 1 day (2 days in a leap year) |
| Business days in a year | Usually 260 or 261 (about 250 after US federal holidays) |
| Days in a quarter | 90–92 |
| Average days in a month | 30.44 |
| Next leap day | February 29, 2028 |
Frequently asked questions
How do I calculate the number of days between two dates?
Enter a start date and an end date above. The calculator counts every calendar day from the start date up to the end date. For example, January 1 to January 31 is 30 days, or 31 days if you include the end date.
Should I include the end date?
Include the end date when both the first and last day count, for example hotel nights vs. days of a trip, a 5-day course, or a leave period. For deadlines, ages and "how many days until" questions, leave it off.
How are business days counted?
Business days are Monday through Friday. Tick "Exclude US federal holidays" to also skip holidays like Thanksgiving and Christmas (using the observed date when a holiday falls on a weekend).
How many days are in a year?
365 days in a common year and 366 in a leap year. Leap years are divisible by 4, except century years not divisible by 400 (so 2000 was a leap year, 2100 won't be).
Does the calculator handle leap years and daylight saving time?
Yes. It counts calendar days, so leap days are included and daylight saving changes don't cause off-by-one errors.
What date is 90 days from today?
Use the "Add or subtract days" tool on this page: it starts from today, adds 90 days and shows the exact date and weekday instantly. Tap "90 days from today" for a one-click answer.
How do I add business days to a date?
In the Add or subtract days tool, choose Days and tick "Count business days only". The calculator skips Saturdays and Sundays. It also warns you if the result lands on a US federal holiday.
What happens when I add months to the 31st?
If the target month is shorter, the calculator uses that month's last day. For example, January 31 plus one month is February 28 (or February 29 in a leap year).
Can I share a result?
Yes. The page address updates as you type, so you can copy the link and send it; the other person sees the same dates and result.
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February 14, 2027Last reviewed: Wednesday, September 30, 2026. All calculations run in your browser; nothing you enter is sent to a server.