This date difference calculator finds the exact gap between any two dates - past, future, or one of each. Enter a start date and an end date and you'll instantly get a full breakdown in years, months and days, plus the total in weeks and days. It works as a days-between-dates calculator for counting how long a project ran, a date duration calculator for measuring an event's length, and a "how many days until date" tool for anything you're counting down to, all in one page.
The calculator works the same way you'd count on a physical calendar. It starts from your first date and steps forward, counting every full year until it would overshoot the end date, then every full month, then the remaining days. That years/months/days figure is the calendar-accurate duration between the two dates. Separately, it also works out the flat total number of days between the dates, then divides that by seven to give a whole-weeks-plus-remainder figure. Because it works on real calendar dates rather than a fixed 30-day-month or 365-day-year assumption, leap years are handled automatically - a range that crosses 29 February is counted correctly, without you needing to think about it.
It doesn't matter which date you type in first. If the "end" date happens to be earlier than the "start" date, the calculator swaps them automatically and simply tells you it did so - so you always get a positive duration instead of an error. This makes it a flexible time duration calculator for quickly comparing any two dates without worrying about which field is which.
People use this tool as a chronological age calculator when they need an age worked out between two specific dates rather than from today, to count exactly how many days are left until a deadline, contract end date, or trip, to measure the length of employment, a lease, or a subscription period, and to settle simple questions like how many days passed between two historical events. Because the output includes both a years/months/days breakdown and a total-days figure, it covers both "how long, roughly" and "exactly how many days" in a single calculation.
Because a single "how long" question can mean different things depending on context, the result always shows more than one way to read the gap. Alongside the years/months/days breakdown, you get the same span expressed as a total number of days and as whole weeks plus a leftover number of days. That means the same calculation can answer "how many days until date X" for a countdown, "how many weeks" for something like a pregnancy or project timeline, and "how many years, months and days" for a more human-readable duration - all from the two dates you entered once.
Like every calculator on this site, the date difference tool runs entirely in your browser - no dates are sent anywhere, there's nothing to install, and there's no limit on how many times you can use it. It's free to calculate date difference as often as you need, on any device.