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Calculation details
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What does this calculator estimate?
Date difference calculator: find the exact days, weeks, months, and years between two dates for deadlines, ages, and project timelines. Free, no signup.
How this calculator works
Formula
Elapsed days = end date - start date in whole days, expressed as weeks and approximate months.
Worked example
January 1 to December 31, 2026: 364 days, 52 weeks, about 11.96 months, measured forward.
Frequently asked questions
What is a date difference calculator?
A date difference calculator is a web tool that computes the number of days, weeks, months, or years between two dates you enter.
Do I need to create an account to use the date difference calculator?
No. The date difference calculator is a no-signup, browser-based tool , it runs entirely in your browser and never requires an account or personal data.
How does the date difference calculator handle leap years?
The date difference calculator automatically accounts for leap years and varying month lengths, ensuring accurate results between any two dates.
Cite this tool
BoringToolsKit. “Date Difference Calculator.” boringtoolskit.com/date-difference-calculator/. Free to reference in articles, syllabi, and answer posts with a link.
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Worked example: January 15 to March 15, 2024
Take start 2024-01-15 and end 2024-03-15. Both parse as local midnight, so the span is 60 days: 16 left in January (31 - 15), 29 in leap February 2024, 15 in March, total 16 + 29 + 15 = 60.
The other three lines divide 60 by a fixed constant and round to 2 decimals. Weeks: 60 / 7 = 8.571428..., displayed 8.57. Months: 60 / 30.436875 = 1.971293..., displayed 1.97. Years: 60 / 365.2425 = 0.164274..., displayed 0.16. Direction reads forward because the end timestamp is greater than or equal to the start. Swap the dates and the magnitudes hold at 60 days, 8.57 weeks, 1.97 months, 0.16 years; only the direction line flips to backward, since the sign is taken before the absolute value.
Boundary cases and what the rounding hides
Identical dates return 0 days and 0.00 on all three lines. A 1-day span shows 0.14 weeks, 0.03 months, 0.00 years, so sub-7-day spans read as zero in the years line. Exactly 7 days is the only whole-week hit: 1.00 weeks, 0.23 months, 0.02 years. A 365-day gap reads 11.99 months, 1.00 years; a 366-day leap gap reads 12.02 months, still 1.00 years, because 365.2425 absorbs the extra day.
The month figure is an average, not a calendar count, so it drifts against real billing. January 31 to February 28 is 28 days: 4.00 weeks, 0.92 months, 0.08 years, yet people call that one calendar month. February 28 to March 1 is 1 day in 2023 (0.03 months) but 2 days in 2024 (0.07 months) because of the leap day. Resolution stops at whole days: the count is Math.round-ed to an integer before the other lines divide it. Inputs are local midnight, so the only sub-day variation is DST: a one-day span is 23 hours (0.958 day) in spring, 25 hours (1.042 day) in fall. Both round back to 1, so the count survives, but nothing finer than a day has an output line.