Whether you're planning a project timeline, calculating a contract term, or just curious how many days until an event, this calculator finds the exact difference between two dates, expressed in days, weeks, and a calendar-accurate months/days breakdown.
How the calculation works
The total day count is found by taking the difference between the two dates in milliseconds and converting to days. The months/days breakdown counts full calendar months first, then the remaining days, which is more meaningful than dividing total days by 30.
Worked example
From March 1, 2026 to April 15, 2026: that's 45 total days, or 6 weeks and 3 days, or equivalently 1 month and 14 days in calendar terms.
Common uses
- Project planning: finding the exact duration between milestones.
- Contracts and leases: calculating notice periods or contract terms.
- Event countdowns: finding how many days remain until a wedding, trip, or deadline.
- Billing and finance: calculating interest-free periods or prorated charges based on exact day counts.
See our full guide on the three ways to measure a date range — calendar days, business days, and calendar-accurate years/months/days — and why they can legitimately disagree.
Common mistakes
- Off-by-one errors. Whether to count the start date, end date, both, or neither depends on context — this calculator counts the number of days elapsed between the two calendar dates.
- Dividing days by 30 to estimate months. Calendar months vary from 28 to 31 days, so a calendar-based months/days breakdown is more accurate than a flat division.
Frequently asked questions
How many days are between two dates?
Subtract the earlier date from the later date; the result in milliseconds is converted to whole days.
Does this calculator account for leap years?
Yes. Because it works from actual calendar dates rather than a fixed 365-day year, leap years are handled automatically and correctly.
Why does the months/days figure differ from dividing total days by 30?
Calendar months vary in length from 28 to 31 days, so counting full calendar months first, then remaining days, gives a more accurate breakdown than an approximate 30-day division.