Date Calculator
Find the days between two dates, or add and subtract days from a date — instantly, with leap years handled correctly.
Use a positive number to move forward, a negative number (e.g. -14) to move backward.
Results are based on calendar days only. For a legal or contractual deadline, confirm the exact counting method (calendar days vs. business days) with the relevant document or a second source before relying on it.
How it works
Choose your mode
"Days between dates" for two known dates, or "Add or subtract days" for one date plus an offset.
Enter your dates
Use the date pickers so there's no room for a typing mistake.
Read the result
Get the exact day count or resulting date, calculated instantly as you change any field.
What people use a date calculator for
Counting days by hand invites mistakes — a calculator handles it in one step.
Contract deadlines
Project due dates
Expiration dates
Countdown to an event
Time since an event
A few things worth knowing about this calculator
Counting days on a paper calendar is easy to get wrong the moment a range crosses a month with a different number of days, or a February that may or may not have 29 days. A date calculator sidesteps all of that by working from real calendar dates instead of a fixed count — so a leap year or a run of short months doesn't throw the result off by even a day.
The two modes here solve different problems, and it's worth pausing to confirm which one you actually need before trusting the number. "Days between dates" answers "how far apart are these two dates" when you already know both of them. "Add or subtract days" answers a different question — "what date do I land on if I move a certain number of days from here" — which is the one you want when you know a start date and a duration but not the end date yet, like a 30-day return window or a 90-day notice period.
When a result actually matters — a legal notice period, a contractual deadline, an official due date — it's worth verifying it a second way before acting on it. Count manually on a calendar for shorter spans, or cross-check against another tool for longer ones, and confirm whether the days in question are meant to be calendar days or business days, since agreements don't always define that the same way.
Frequently asked questions
How do I find the number of days between two dates?
Switch to the "Days between dates" mode, pick a start date and an end date, and the total number of days appears instantly, along with a years/months/days breakdown for longer spans.
How do I add or subtract days from a date?
Switch to the "Add or subtract days" mode, pick a base date, and enter the number of days — a positive number moves forward, a negative number moves backward. The resulting date and its day of the week appear instantly.
Does this calculator handle leap years correctly?
Yes. Both modes work from actual calendar dates rather than a fixed day count per year, so leap years and different month lengths are accounted for automatically.
How do I know I'm using the right mode?
If you have two known dates and want to know the gap between them, use "Days between dates." If you have one known date and want to move a number of days forward or backward from it, use "Add or subtract days." The two modes ask for different inputs, so the active tab makes it clear which one is in use.
Can I use this for legal or contractual deadlines?
It can help estimate a date or a day count, but for anything with real consequences — a legal notice period, a contract deadline — verify the result with a second method or the relevant document's own rules before relying on it, since some agreements define "days" differently (business days vs. calendar days, for example).
Is this date calculator free to use?
Yes, completely free, with no account or sign-up, and it runs entirely in your browser.