Date Calculator – Days Between Dates

How to Use the Date Calculator

The calculator has two modes. Days between dates answers questions like “how many days until my holiday?”, “how old is this invoice?” or “how many working days does this project have?”. Add / subtract days answers “what date is 90 days from today?” or “what was the date six weeks ago?”. Pick a mode, enter your dates, and the answer appears immediately — there is no button to press.

• Days between dates — choose a start and an end date. You get the total number of days, the same span in weeks, in years/months/days, in business days and weekend days, and in hours, minutes and seconds. If the end date is earlier than the start date, the result is shown as a negative span.
• Add / subtract — choose a date, then any combination of years, months, weeks and days. The result shows the new date with its weekday, ISO week number and day of the year.
• Holidays — paste your public holidays or days off into the holiday list, and they are left out of every business-day count.
• Share — Copy link to this calculation copies a URL that reopens the page with your dates filled in, handy for a deadline you want to send to a colleague.

Should the End Date Be Included?

By default the calculator counts the days you need to get from the start date to the end date, which is what most people mean by “days between”. From Monday to Friday of the same week that is 4 days. If you want to count every calendar day in the range, including both the first and the last one — for example the number of days a hotel booking, a trip or a rental covers, or a contract period that runs “from 1 March to 31 March inclusive” — tick Include the end date. Monday to Friday then counts as 5 days, and 1 to 31 March as 31 days instead of 30.

How Months and Years Are Counted

Days and weeks are exact, but months are not all the same length, so “how many months between two dates” needs a rule. This calculator counts whole calendar months first and then the days that are left over, the same way you would count on a wall calendar: from 15 January to 20 March is 2 months and 5 days. When the start date is the last days of a long month, the month step lands on the last day of the shorter month — one month after 31 January is 28 February (or 29 February in a leap year), and adding one year to 29 February 2024 gives 28 February 2025. Leap years follow the Gregorian rules: a year is a leap year if it is divisible by 4, except century years, which are only leap years if divisible by 400 (2000 was, 2100 will not be).

Calculations work on calendar dates, not on clock times, so daylight-saving time changes never make a day 23 or 25 hours long here. The hour, minute and second figures are simply the number of days multiplied out.

Business Days and Holidays

Business days (also called working days or weekdays) are Monday to Friday. In Days between dates, they are counted the same way as the total: the start date counts and the end date counts only when Include the end date is ticked. In Add / subtract, tick Count “Days” as business days to move forward or backward by working days only — 10 business days after a Friday is the Friday two weeks later, and a deadline never lands on a weekend.

Public holidays differ by country, state and even company, so the calculator does not guess them. Instead, paste the dates that apply to you into the holiday list. Holidays that fall on a Saturday or Sunday are ignored, because those days are already excluded.

Common Questions This Calculator Answers

• Countdowns — days until a birthday, a wedding, a holiday, an exam or the end of the year (use Start = today).
• Deadlines — the date 30, 60 or 90 days after an invoice, a notice period of three months, or 10 business days for a delivery.
• Age and anniversaries — exact age in years, months and days, or how many days you have been alive.
• Projects and sprints — the number of working days between two milestones, minus public holidays.
• Pregnancy and health — 40 weeks from a given date, or how many weeks have passed since a date.

Features

• Days, weeks, months and years — every span shown in all units at once.
• Business days with your own holidays — no hidden assumptions about which country you live in.
• Add and subtract years, months, weeks, days or business days in one step.
• Weekday, ISO week and day of year for every result date.
• Shareable link — the URL always reflects your current inputs.
• 100% client-side — your dates never leave your browser.

Frequently Asked Questions

How do I calculate the number of days between two dates?

Enter both dates in the Days between dates mode. The calculator subtracts the start date from the end date and shows the result in days. Without the end date included, 1 January to 31 January is 30 days; with the end date included it is 31 days.

Does the calculator count the start date and the end date?

It counts the start date but not the end date by default, which gives the number of days you need to get from one date to the other. Tick “Include the end date” to count both, which adds one day.

How are business days counted?

Business days are Monday to Friday. Saturdays, Sundays and any holidays you enter in the holiday list are skipped. The start date is counted and the end date only when you choose to include it.

What date is 90 days from today?

Switch to the Add / subtract days mode, keep today as the start date, and enter 90 in the Days field. The result shows the date together with its weekday. Use the business-days option if weekends should not count.

What is one month after 31 January?

There is no 31 February, so the calculator moves to the last day of February: 28 February, or 29 February in a leap year. Every month step works this way, which is also how most spreadsheets and programming languages handle it.

Are public holidays included automatically?

No, because holidays depend on your country, region and employer. Paste the dates that apply to you into the holiday list, one per line, and they are excluded from all business-day counts.

Are my dates sent to a server?

No. All calculations run entirely in your browser with JavaScript. Nothing is transmitted or stored; only if you copy a share link are your dates written into that link.