Date Calculator
The Date Calculator adds or subtracts days, weeks, months, or years from any date. Useful for scheduling, project planning, legal deadline calculations, pregnancy due-date tracking, and anything else that requires calendar math.
How Date Math Works
For days and weeks, the calculator simply adds or subtracts the correct number of days. For months, it adds to the month number and adjusts the day if the resulting month is shorter (e.g., Jan 31 + 1 month = Feb 28 or 29). For years, it adds to the year number and adjusts for leap years when going from Feb 29.
Common Uses
Common uses include: calculating a 30-day return deadline, finding a project due date, counting backwards from a wedding to deadlines, calculating a pregnancy due date (280 days from last menstrual period), figuring out when a lease starts or ends, and computing anniversaries far in the future.
Frequently Asked Questions
How accurate is this calculator?
The calculator uses standard JavaScript math, which is accurate to approximately 15 significant decimal digits.
Is this calculator free?
Yes, completely free with no signup required.
Does it save my inputs?
Values are kept during your session but are not saved between visits. You can bookmark a URL with specific parameters to return to.
Can I use this on mobile?
Yes, the calculator is fully responsive and works on phones, tablets, and desktop browsers.
Does the result include weekends?
Depends on the calculator. Date calculators show both calendar days (including weekends) and business days (excluding weekends).
How is this different from Google calculator?
This calculator shows the step-by-step formula and provides specialized features (business days, mixed fractions, percent change) that Google calculator does not.
Can I share my calculation?
Copy the URL from the browser bar to share the current calculation state.
Where can I find more calculators?
See our complete list at /calculator.