Date Calculator
Calculate the difference between two dates, or add and subtract time from any date.
All calculations happen locally in your browser — nothing is uploaded, stored or tracked.
Choose a mode
Difference between two dates, or add/subtract from a date.
Enter the dates or amounts
Use the date pickers and number fields.
Read the result
Including weekdays-only counts when relevant.
What Is a Date Calculator?
A date calculator answers two common questions: "how many days are there between these two dates?" and "what date is it X days from now?" Both look simple but trip over calendar rules — months of different lengths, leap years, and daylight-saving-free date arithmetic.
The difference mode reports the span in days, weeks, months and years simultaneously, including the total days excluding weekends if you want a business estimate. The add/subtract mode starts from any date and moves forward or backward by a chosen number of days, weeks, months or years.
How Dates Are Counted
The difference between two dates is the number of midnight-to-midnight steps between them. Adding months to a date uses calendar-month arithmetic: 31 January plus one month is 28 February (or 29 in a leap year), not 3 March. This is how most official systems behave.
Your data never leaves your device.
Every calculation on this site runs in your browser using vanilla JavaScript. Nothing is uploaded, stored or tracked.
- 100% local, client-side calculations
- No data stored on any server
- No tracking, no analytics, no ads scripts
- Works offline once loaded
Frequently Asked Questions
How do I count days between two dates?
Enter both dates in the difference mode. The calculator counts every calendar day between them, including the end date's difference from the start.
What date is 90 days from today?
Enter today as the start date and 90 in the days field — the calculator handles month lengths automatically.
How many days are there between January 1 and March 1?
In a non-leap year, 59 days (31 + 28); in a leap year, 60. The calculator accounts for this automatically.
Does the calculator handle leap years?
Yes — leap years are built into the calendar arithmetic, including century years that are not divisible by 400.
How do I count business days between two dates?
Use the "exclude weekends" option in difference mode for an estimate. Public holidays vary by country and are not included.