Date Calculator
Calculate date differences or add and subtract time from any date
Results will appear here
About Date Calculator
All calculations use the native JavaScript Date object and run entirely in your browser — no data is sent to any server.
How to Use This Tool
- To find the difference between two dates, select "Date Difference", enter a start date and an end date, then click "Calculate".
- The result shows the precise difference in years, months, days, hours, and total days.
- To add or subtract time from a date, select "Add/Subtract", choose a base date, enter the number of days/months/years, and pick the operation.
- The resulting date is displayed immediately, accounting for leap years and varying month lengths.
Common Use Cases
- Calculating your exact age in years, months, and days from your date of birth.
- Finding how many days remain until a project deadline, exam, or event.
- Determining contract durations or notice periods for employment agreements.
- Calculating pregnancy due dates by adding 40 weeks to the first day of the last menstrual period.
- Figuring out what date falls 30, 60, or 90 days from today for invoicing and payment terms.
Frequently Asked Questions
Does the calculator account for leap years?
Yes. All calculations use JavaScript's native Date object, which correctly handles leap years, daylight saving time transitions, and the varying lengths of months.
Can I calculate business days (excluding weekends)?
The current version calculates calendar days. Business day calculation, which also excludes public holidays, varies by country and is planned as a future enhancement.
What date formats are accepted?
The date inputs use your browser's native date picker, which formats dates according to your locale. Internally, dates are handled in the ISO 8601 format (YYYY-MM-DD).
How far in the past or future can I calculate?
The calculator can handle any date within JavaScript's safe date range, which covers millions of years in both directions from the Unix epoch — well beyond any practical need.