Date Duration Calculator
How many days between two dates? Find out instantly.
Counting days between dates by hand is error-prone — months have different lengths and leap years sneak in.
How to use
- Pick a start date and an end date.
- Click Calculate for days, weeks and a full breakdown.
- Order does not matter — it always shows the gap.
About this tool
Common uses: pregnancy week tracking, project timelines, "how many days until my trip", and age-style calculations.
Dates are processed locally; nothing is uploaded.
How it works
Counting the days between two dates is a subtraction: the tool converts each date to a day number on the proleptic Gregorian calendar (our calendar extended backwards before its 1582 debut) and subtracts. January 1 to January 2 is 1 day — the count measures 24-hour steps between midnights, not the dates themselves.
There are two conventions. Exclusive counting (the default here) gives the number of full days between the dates — what you want for age-in-days or days-until-deadline. Inclusive counting adds one to include both endpoints, which is what hotels and project billers usually mean by ‘days’. If you need inclusive, just add 1.
Weeks, months and years are derived, not counted: weeks are total days divided by 7, while months and years follow the calendar. That is why the same 60-day span can read as ‘about 2 months’ in March–April but ‘under 2 months’ in February–March — February is simply shorter.
Worked examples
Project timeline: Kickoff Monday Jan 6, 2025 to launch Friday Mar 14, 2025: 67 days, or 9 weeks and 4 days. Billing per calendar day including both endpoints? That is 68 days.
Age in days: Born Jun 12, 1990 → Oct 5, 2026: 13,264 days. A fun number for a milestone birthday post.
Quick reference
| Unit | Equals |
|---|---|
| 1 week | 7 days |
| 1 fortnight | 14 days |
| Average month | 30.44 days |
| Average year | 365.25 days (leap years included) |
| 1 decade | 3,652.5 days |
Frequently asked questions
Does it count the start and end day?
It measures the gap between the two dates — e.g. Monday to Wednesday is 2 days.
Does it handle leap years?
Yes, all math uses real calendar dates.
Are my dates stored?
No — everything runs in your browser.
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