“How many days until…?” and “How long ago was…?” are the same question asked in two directions. This calculator counts the calendar days between any two dates and breaks the gap down into the units people actually use: years and months, weeks, working days and even seconds.
How to use the date difference calculator
- Pick a start date and an end date. Either can be in the past or the future.
- Tick Include the end date if both dates should be counted (an inclusive count).
- Read the total on the tape, along with the breakdown in years/months/days, weeks and business days.
How the days are counted
The calculator converts both dates to day numbers on the Gregorian calendar and subtracts them. Working in whole calendar days avoids daylight-saving surprises, where a single day can be 23 or 25 hours long.
Inclusive vs. exclusive counting
| Situation | Count | Example: Mon 3rd → Fri 7th |
|---|---|---|
| Nights in a stay, loan interest days, “days until” | exclusive | 4 days |
| Days of an event, vacation days taken, a “Day 1 to Day N” plan | inclusive | 5 days |
Examples
- Due-date planning: from January 15 to April 30, 2026 is 105 days — 15 weeks exactly.
- A 90-day window: start on a date and use the date calculator to add 90 days and find the deadline.
- Countdowns: for a live ticking clock to a date and time, use the countdown timer.
Counting days by hand
You can check the calculator’s answer with a simple month-by-month walk:
- Count the days left in the start month (for an exclusive count, subtract the start day from the month’s length).
- Add the full length of every month in between.
- Add the day number of the end date.
From March 18 to June 2: March has 31 − 18 = 13 days left, April adds 30, May adds 31, and June adds 2, for 76 days. Tick “include the end date” and the answer becomes 77.
Common durations at a glance
| Duration | Days | Weeks |
|---|---|---|
| 30 days | 30 | 4 weeks 2 days |
| 60 days | 60 | 8 weeks 4 days |
| 90 days | 90 | 12 weeks 6 days |
| 6 months (Jan 1 → Jul 1, common year) | 181 | 25 weeks 6 days |
| 1 common year | 365 | 52 weeks 1 day |
| 1 leap year | 366 | 52 weeks 2 days |
| 40-week pregnancy | 280 | 40 weeks |
Calendar facts that affect the count
- Months have 28, 29, 30 or 31 days, so “one month” is not a fixed number of days.
- A common year has 365 days (52 weeks + 1 day); a leap year has 366.
- The Gregorian calendar repeats every 400 years, which contain exactly 146,097 days.
Frequently asked questions
Does the count include both the start and end date?
By default it counts the days from the start date up to, but not including, the end date — the same way you would count nights in a hotel stay. Tick "Include the end date" to add one day when you need to count both dates, as for an event that runs Monday through Friday.
How are leap years handled?
Dates are counted on the real calendar, so February 29 is included in leap years (2024, 2028 and so on). Years divisible by 100 are not leap years unless they are also divisible by 400.
Why are business days different from total days?
Business days count Monday to Friday only. Public holidays vary by country and employer, so they are not removed automatically — subtract them yourself if they apply.
How does the calculator show months when months have different lengths?
The years-months-days figure steps through the calendar the way people count, so January 31 to March 1 is 1 month and 1 day in a non-leap year. The total-days figure is always exact.