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Date Calculator

Add or subtract years, months, weeks and days from any date, with a business-day mode and explicit month-end clamping.

Related tools

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Date Pattern GeneratorList palindrome, repdigit, sequential and square-root dates over any year range, labelled per date format (DD/MM/YYYY, MM/DD/YYYY, YYYY-MM-DD).Halfway Date CalculatorFind the exact midpoint between two dates and times, down to the leftover hours, plus quarter and third markers and the elapsed/remaining split.Add or subtract days from a dateFind the date a number of days before or after a starting date.Date difference calculatorCount the days, weeks and months between two dates.Days until date calculatorCount the number of days from today until a future date.Julian Date converterConvert a calendar date and time to the astronomical Julian Date (JD) and back, live. It also returns the Modified Julian Date (MJD = JD − 2400000.5) and the Unix timestamp, and lets you pick the Gregorian or Julian calendar for dates before the 1582 reform. Astronomer-grade: noon UTC on 1 January 2000 comes out to exactly JD 2451545.0.Anniversary CalculatorHow long has it been, exactly? Years, months and days elapsed since a wedding, a first date, a friendship or a first day at work, the total in days, weeks and hours, the countdown to the next anniversary, the milestones coming up (10 000 days, silver, gold) and — for weddings — the traditional and modern gift for that year, in both the British and the American lists.Autumnal Equinox CalculatorGet the exact instant of the autumnal equinox and of all four seasonal markers for any year, in UTC and in your own offset, with northern and southern naming and the length of each astronomical season.

Date Calculator works straight from this page — free, instant, nothing to install. Its place is under Dates & time; Date Pattern Generator and Halfway Date Calculator answer the questions closest to this one.

How to use it

  1. Open the tool — no signup or install needed.
  2. Enter your input or adjust the available options.
  3. Get your result instantly, then copy or download it.

Frequently asked questions

What does Date Calculator do?

Add or subtract years, months, weeks and days from any date, with a business-day mode and explicit month-end clamping.

When would I actually use this?

Answering a scheduling question exactly: how many working days until a deadline, what date falls sixty days out, and what time that is for a colleague elsewhere.

What is the most common mistake?

Counting days by subtracting dates and forgetting whether the endpoints are included. Inclusive and exclusive counts differ by one, which is the difference between meeting a deadline and missing it.

How is Date Calculator different from Date Pattern Generator?

They sit next to each other but answer different questions: Date Pattern Generator is the one to open when you need it to list palindrome, repdigit, sequential and square-root dates over any year range, labelled per date format (DD/MM/YYYY, MM/DD/YYYY, YYYY-MM-DD). Pick whichever matches what you're starting from — both are free.

Is there a tool for the next step?

Halfway Date Calculator is the closest one after this: Find the exact midpoint between two dates and times, down to the leftover hours, plus quarter and third markers and the elapsed/remaining split.

What else is worth having open alongside it?

Add or subtract days from a date and Date difference calculator — they come up in the same task often enough to be worth a second tab.

Where do the figures come from?

Calendar arithmetic follows the proleptic Gregorian calendar and the IANA time-zone database, so daylight-saving transitions and leap years are handled. Public holidays vary by country and region and are not assumed.

Further reading

All guides →
ExplainerDate Arithmetic Is Harder Than It Looks"One month later" has no single correct answer, and every date library has had to pick one. Month addition is neither associative nor invertible, a day is not always 24 hours, and age is not days divided by 365.25.ExplainerLeap Years: The Rule, the Exception, and the Exception to the ExceptionDivisible by four, except centuries, except centuries divisible by four hundred. The three-line rule exists because the tropical year is not 365.25 days, and the arithmetic behind it explains ten deleted days in 1582 and a calendar that repeats exactly every 400 years.How-toHow to Add or Subtract Days from a DateCount forward to add, backward to subtract, rolling over month ends. Here's how, why month lengths and leap years trip you up, and when weekends count.How-toHow Many Days Until a Date? (With Worked Examples)Count the days until any future date, understand inclusive vs. exclusive counting, and build an accurate countdown you can trust.ExplainerWorking Out an AnniversaryCounting back and counting forward are two different sums, and they disagree by a year on the day itself. What this calculator does with 29 February, what other date libraries do, and where the traditional and modern gift lists actually come from.ExplainerSeconds, Minutes and Hours: How Time Units Fit TogetherThe relationships behind 60 seconds, 60 minutes, 24 hours and 86,400 seconds a day, with quick conversions you can reuse.