Date Duration Calculator
Find the exact duration between two dates, plus date arithmetic.
Duration between two dates
Add or subtract days
What is the Date Duration Calculator?
The Date Duration Calculator tells you exactly how much time sits between any two dates. Pick a start and an end date and you get a calendar-accurate breakdown in years, months and days, plus total days, total weeks and approximate total months. A second mini-tool does date arithmetic: enter a date, add or subtract any number of days, and get the resulting date — handy for deadlines, warranties and project planning.
How to use it
- Choose your start and end dates with the date pickers (the order does not matter).
- Press "Calculate duration" to see the years/months/days breakdown and the totals.
- For date math, enter a date and a number of days, choose Add or Subtract, and press "Calculate date".
How the breakdown works
The years/months/days breakdown follows the calendar: it counts whole years, then whole months, then remaining days, correctly handling different month lengths and leap years. Total days is the exact day count between the dates. Total weeks is total days divided by seven, and total months is an approximation (total days / 30.437, the average month length) — the breakdown above it is the precise figure to rely on.
Common uses
- Project timelines: how long between kickoff and deadline.
- Contracts and warranties: exact coverage periods.
- Event planning: days until a wedding, launch or exam.
- Deadlines: what date is 90 days from today.
Private by design
All calculations happen in your browser. No dates you enter are uploaded or stored anywhere.