Find the difference between two dates or calculate a new date by adding and subtracting years, months and days.
Start Date
End Date
Base Date
Add or subtract (use negative to subtract)
Time moves in one direction, but planning requires you to think in all of them. How many days until a contract expires? How much time has actually passed since a particular date you remember but cannot easily measure? What date will it be exactly six months from today? These are the kinds of questions that come up in work, finance, legal matters, and everyday life — and they are surprisingly awkward to answer accurately without a proper tool. This date calculator handles both types of problems cleanly: finding the gap between two dates, and finding a new date by adding or subtracting a period of time.
Most date tools online solve one problem at a time. This page gives you both in a single place.
Calculates the exact gap between any two dates in years, months, and days — along with the total number of days and weeks between them. You pick a start date and an end date, and the calculator works out the precise interval accounting for leap years, varying month lengths, and all the irregularities of the calendar.
Takes any date as a starting point and lets you add or subtract any combination of years, months, and days to arrive at a new date. Need to know what date falls exactly 90 days from today? Or what date was 18 months before a specific event? Use positive numbers to move forward in time and negative numbers to move backward.
Date arithmetic sounds like a niche need until you realise how often it comes up in ordinary life.
Legal and contractual deadlines
Lease agreements, service contracts, warranties, and loan documents almost always specify durations in months or years from a signing date. Knowing the exact expiry date and how many days remain matters for renewals, notices, and legal compliance. A one-day error on a notice period can have real consequences.
Financial planning
Fixed deposits mature on a specific date. Tax filing deadlines, advance tax due dates, and financial year boundaries all require precise date arithmetic. Knowing exactly how many days remain in a financial year or until a payment is due helps with planning that goes beyond rough estimates.
Pregnancy and health tracking
Due date calculations, vaccination schedules, and medication cycles all depend on counting forward from a known date by a specific number of weeks or months. These calculations need to be exact, and mental arithmetic with calendar months of varying length is unreliable.
Project management and work deadlines
Sprint durations, project milestones, notice periods, and probation end dates are all date-based. Calculating exactly when a 90-day probation ends, or how many days exist between a project kick-off and a deadline, requires the kind of precision this tool provides.
Age and anniversary calculations
How old will someone be on a specific future date? How long have two people been together? How many days until a major anniversary? These are personal but genuinely common questions, and getting the answer right — especially across year boundaries — is harder than it looks without a calculator.
Visa and immigration timelines
Visa validity periods, permitted stay durations, and re-entry restrictions are all date-dependent. Overstaying a visa by even one day has serious consequences. Calculating the exact last permitted day from a known entry date and permitted stay period is exactly what this tool is built for.
Calendar months have different lengths — 28, 29, 30, or 31 days depending on the month and whether it is a leap year. This means that adding "one month" to a date is not the same as adding 30 days. January 31 plus one month is February 28 or 29, not March 2 or 3. This is a subtle but important distinction that catches people out constantly when they try to calculate date intervals by hand or with a basic calculator.
Leap years add another layer of complexity. A year is a leap year if it is divisible by 4 — except for years divisible by 100, which are not leap years, unless they are also divisible by 400. This rule means that 2000 was a leap year, 1900 was not, and 2100 will not be. Any calculation that crosses a February in a year near these boundaries needs to account for this correctly.
This calculator handles all of these edge cases automatically. The result you see is mathematically precise regardless of which months or years are involved.
The calculator finds the exact difference between two dates expressed as complete years, remaining months, and remaining days — the same way you would describe someone's age. A person born on 15 March 2000 and measured on 20 September 2026 is not simply 26 years old — they are 26 years, 6 months, and 5 days old. This level of precision matters when the calculation is for something more consequential than a birthday.
Total days
Gives you the raw interval as a single number — useful when counting down to an event, calculating interest on a daily basis, or determining whether a deadline has passed.
Total weeks
Useful for scheduling and project planning where work is organised in weekly cycles. Knowing the week count alongside the days gives you a more actionable view of the interval.
This mode takes a starting date and applies an offset — positive to move forward, negative to move backward — expressed in any combination of years, months, and days. The calculation applies the offset in the correct order: years first, then months, then days. This order matters because month lengths vary and applying days before months can produce subtly incorrect results.
Month-end edge cases are handled correctly. Adding one month to 31 January gives 28 or 29 February, not an overflow into March. This is the behaviour you would expect from a calendar, and it is what this calculator delivers.
Long-term agreement end date
Starting from 1 January 2025, adding 3 years, 6 months, and 15 days gives 16 July 2028 — useful for calculating the end of a long-term contract or financial commitment.
Historical interval
The gap between 14 August 1947 and today spans decades, months, and days precisely — the kind of calculation that is instantly meaningful but impossible to do reliably in your head.
Backward notice period
Adding negative 90 days to any date gives you the date three months prior — useful for calculating notice periods that work backward from a known end date.
Probation end date
A joining date of 10 April 2025 with a 6-month probation gives an end date of 10 October 2025 — instantly calculated without counting months on your fingers.
Every calculation runs entirely within your browser. No dates you enter are stored, transmitted, or logged anywhere. The tool works offline once loaded and requires no account, no registration, and no personal information of any kind.
Enter the start date and end date into the date calculator to find the exact difference in years, months, days, total days, and weeks.
Yes, using the Add/Subtract feature, you can add or subtract years, months, and days to a base date to get the exact resulting date.
Yes, the calculator automatically accounts for varying month lengths and leap years, giving precise results for all date calculations.
Absolutely. This calculator is ideal for determining exact dates for contracts, probation periods, visa timelines, and financial deadlines.
No, all calculations run locally in your browser. Your dates are not stored, transmitted, or logged.
Yes, the date calculator provides total weeks along with years, months, and days for a complete interval analysis.
Yes, the tool is fully responsive and works seamlessly across mobile, tablet, and desktop screens.
The calculator adjusts correctly for month-end edge cases. For example, adding one month to January 31 will give February 28 or 29 depending on the year.
* This tool is intended for general planning and reference. For legal, medical, or financial matters where date precision is critical, always verify results with a qualified professional.