Date Calculator

Two calculators on this page

They are separate tools, each with its own button and its own answer, so you can use one without clearing the other. Days Between Two Dates measures the span from a start date to an end date — useful for counting down to an event, tracking a project timeline or checking someone's age on a specific day. Add to or Subtract from a Date shifts a single date forward or back by any combination of years, months, weeks and days, handy for deadlines, due dates and return-by dates. Either one can count business days instead of calendar days.

Finding the days between two dates

1. Use the Days Between Two Dates calculator at the top.
2. Enter a start date and an end date.
3. Press Calculate to see the total days, the span in weeks and days, and a breakdown in years, months and days.

The two dates are order-independent: put the later one first and the tool still reports the same span, simply noting the direction rather than flagging an error. Two identical dates return zero.

Counting days: the endpoint question

"How many days between" almost always means the difference — the later date minus the earlier one. From July 1 to July 10 that is 9 days. If you actually want to include both the first and last day, as when counting the days of a trip, tick Include the end day and the count becomes 10. Deciding which you need up front avoids the classic off-by-one error.

Counting business days

Tick Count business days only and the count drops the weekends, which is what you want for delivery windows, notice periods, court deadlines and anything else measured in working days. Tick Also skip US federal holidays and the eleven federal holidays come out too.

Holidays are counted on the day they are observed, not the date in the statute. A fixed-date holiday that lands on a Saturday is observed the Friday before, and one on a Sunday the Monday after — so Independence Day 2027 falls on a Sunday and the day off is Monday July 5. Juneteenth is only counted from 2021, the year it became a federal holiday, so historical spans are not quietly shortened.

In the second calculator, business days are a count of working days, so the amount goes in the Days box on its own. The start day itself is never counted: three business days from a Friday is the following Wednesday, and asking from the Saturday lands on the same Wednesday.

Adding or subtracting from a date

1. Use the Add to or Subtract from a Date calculator below it.
2. Enter a start date and choose add or subtract.
3. Fill in any combination of years, months, weeks and days. A box left blank counts as zero; at least one must be filled in.
4. The resulting calendar date appears, with the weekday spelled out.

Because the count is applied straight to the calendar, month lengths and leap days are handled for you — there is no need to work out which months have 30 or 31 days.

What "one month later" means

Months are not all the same length, so adding one to the 31st has to land somewhere. The answer here is the last day of the target month: one month after January 31 is February 28, or February 29 in a leap year, rather than rolling over into March. That is what a calendar does when you page forward a month, and it keeps the step reversible.

Years and months are applied first, then weeks and days. That order matters at month ends: one month and one day after January 31 is March 1 — the month step clamps to February 28 first, and the day is added to that.

A worked example

From 15 January 2026 to 10 August 2026 is 207 days — that is 29 weeks and 4 days, or 6 months and 26 days in the calendar breakdown, and 147 business days once weekends come out. In the second calculator, adding 90 days to 10 August 2026 lands on 8 November 2026.

Accurate calendar math

Because months vary in length and leap years add a day, counting dates by hand is error-prone. This calculator works directly on the calendar, so every result is exact no matter which dates you choose, and the total-day count and the year-month-day breakdown always agree. Looking for an exact age from a birth date instead? Try the age calculator; to add up spans of hours and minutes, use the time calculator.