Date Calculator – Days Between Dates & Add or Subtract Days

How to use Date Difference Calculator

1Under Days between two dates, pick a start and an end date.

2Read the difference in years, months and days, plus total days, weeks and business days (Monday–Friday).

3Tick Include the end date if both the first and last day should be counted, as with event or rental days.

4To find a future or past date, use Add or subtract — choose a date, + or −, an amount and a unit.

Count days between dates

How many days until a holiday, a deadline or a due date? How many working days does a project have? This date calculator answers both kinds of question. Enter two dates to see the difference in years, months and days, the total number of days and weeks, and the number of business days. Or start from one date and add or subtract days, weeks, months or years to find another. It all runs instantly in your browser.

Features

Exact difference in years, months and days.
Total days and weeks plus days.
Business days (Monday to Friday) for project and delivery planning.
Inclusive counting option when both the start and end day should count.
Add or subtract days, weeks, months or years, with correct handling of month ends and leap years.
Dates shown in your language's full format, plus ISO format (YYYY-MM-DD).

Common uses

Deadlines and contracts. Payment terms such as "net 30", notice periods, warranty periods and trial subscriptions are all counted in days or months. Add 30 days to an invoice date to find the due date, or count days to see whether a deadline has passed.

Project planning. Business days give a realistic picture of the time available for work, ignoring weekends.

Travel and events. Count down to a trip, or count the days of a stay. For hotel stays, the number of nights is the difference without the end date; the number of days you are there includes it.

Health and pregnancy. Track days since a start date or count forward by weeks — for example, 40 weeks from a given date.

Legal and HR. Check probation periods, holiday entitlement windows and statutory deadlines. (Always confirm whether a rule counts calendar days or working days, and whether public holidays are excluded.)

How months and years are added

Adding days and weeks is exact. Adding months and years follows the calendar: 15 March plus one month is 15 April. When the target month is shorter, the date moves to that month's last day — 31 August plus one month is 30 September. This matches how most banks, contracts and spreadsheet functions such as EDATE behave.

To calculate someone's age, use the Age Calculator. To work with exact moments in time rather than dates, try the Unix Timestamp Converter.

Frequently asked questions

Does the calculator include the end date?

By default, no — from Monday to Tuesday is one day, the usual way to count durations. Tick Include the end date to count both the first and the last day, which is how hotel nights differ from stay days, or how many days an event runs.

How are business days counted?

Business days are Monday to Friday between the two dates, not including the end date (or including it if you tick the option). Public holidays are not subtracted because they differ by country and region, so remove those manually if needed.

What happens when I add a month to 31 January?

Months have different lengths, so the result is clamped to the last day of the target month — 31 January plus one month is 28 February (or 29 in a leap year). Adding years to 29 February works the same way.

Can the end date be before the start date?

Yes. The calculator swaps them, shows the positive difference, and notes that the dates were reversed.

Are time zones or daylight saving a problem?

No. The calculator works with calendar dates only, not times of day, so daylight-saving changes never add or remove an hour that could shift the result by a day.