Find the exact duration in days, weeks, months, or years between any two dates, with business day support.
Exact durations for typical intervals. Months column uses the average month length (30.44 days).
| From | To | Days | Weeks | Months (approx) |
|---|---|---|---|---|
| 2020-01-15 | 2026-09-04 | 2,424 | 346.29 | 79.6 |
| 2024-01-01 | 2026-09-04 | 977 | 139.57 | 32.1 |
| 1990-06-15 | 2026-09-04 | 13,230 | 1,890.00 | 434.6 |
| 2010-12-25 | 2026-09-04 | 5,732 | 818.86 | 188.3 |
| 1965-07-04 | 2026-09-04 | 22,342 | 3,191.71 | 734.0 |
| 2026-09-04 | 2027-01-01 | 119 | 17.00 | 3.9 |
All intervals calculated on the proleptic Gregorian calendar with full leap-year handling (9 leap days in the 1990→2026 span; 15 in the 1965→2026 span).
A date duration calculator determines the exact amount of time between two calendar dates, breaking the difference down into years, months, weeks, days, and even hours. This is more complex than simply subtracting two dates because months have varying lengths (28, 29, 30, or 31 days) and leap years add an extra day every four years.
The core calculation works by finding the difference between the start date and end date. First, the calculator determines the year difference, then the remaining month difference, and finally the leftover days. For example, the duration between January 15, 2024 and March 20, 2025 is 1 year, 2 months, and 5 days.
Business days are calculated by iterating through each day in the range and counting only Monday through Friday, excluding weekends (Saturday and Sunday). This is particularly useful for project planning, contract terms, and payroll calculations where only working days count.
Common use cases: Calculating project timelines and deadlines, determining lease or rental periods, computing age or anniversary dates, planning countdowns to events, tracking employment tenure, and estimating loan interest periods. Project managers use date duration to allocate resources, while HR professionals use it to determine vacation accrual and seniority.
Leap year consideration: Every year divisible by 4 is a leap year, except for century years (divisible by 100) unless they are also divisible by 400. This means 2024 is a leap year, 1900 was not, but 2000 was. Our calculator automatically accounts for leap years and varying month lengths to provide accurate results.
Tip: When including the end date in your calculation (the "inclusive" option), the total increases by one day. This is common in hotel stays or event planning where both the start and end dates count toward the total duration.
Type the start date and end date. The calculator accepts any dates in the past, present, or future.
Count all days, business days only (excludes weekends), or business days excluding US federal holidays.
Get the result in days, weeks, months, years, hours, minutes, and seconds. The calculator handles month-length differences and leap years.
For related calculations, try our date calculator.
Cross-checked against authoritative formulas (IRS, NIST, ACSM) and updated for 2025/2026 tax years and rates.
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We never collect, store, or transmit your inputs. Every calculation runs locally in your browser.
Each calculator includes the formula, plain-English explanation, and FAQs so you understand the result.
Estimates only. Calculator results are for educational and planning purposes — not professional advice. For binding decisions on taxes, investments, health, or legal matters, consult a qualified professional.
FAQ
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A date duration calculator is a free tool that finds the exact number of days, weeks, months, and years between two dates. Our date duration calculator supports business day mode (excludes weekends) and shows the breakdown in multiple units. The date duration calculator is used for contract terms, lease durations, and project timelines.
How it works
Our date duration calculator lets you calculate the exact number of days, weeks, months, and years between any two dates.
Use the date inputs to pick the start and end dates. The date duration calculator accepts any valid date in the supported range. The start date is included unless you toggle the option.
Toggle business day mode to exclude weekends (and optionally holidays). The date duration calculator shows the count in both calendar and business days. Business day mode is useful for contract and project calculations.
The result shows the total in days, weeks, months, and years, plus the breakdown by unit. The date duration calculator also shows the number of leap years in the range. The share button creates a link with your inputs pre-filled.
Add or subtract days, weeks, months, or years from any date.
Add or subtract days, weeks, months, or years from a start date.
Find the exact age in years, months, and days from a birth date.
Count days between two dates with optional business-day mode that skips weekends.
Find the weekday for any date plus ISO week number, day of year, and days until.