Free Date to Date Calculator Online
Enter a start date and end date and this free online date to date calculator instantly returns the exact duration in days, weeks, months, and years — plus a workday estimate. Completely free, no sign-up needed.
Total Duration
How the Free Date to Date Calculator Works
This free date to date calculator finds the exact interval between two calendar dates. Under the hood it uses JavaScript's Date object, which stores timestamps in milliseconds. The difference between the two timestamps is converted to whole days by dividing by 86,400,000 (the number of milliseconds in a day). Use it free online — no spreadsheet required.
From the total days, the calculator derives the other units. Weeks are straightforward: total days divided by 7. Approximate months use 30.4375 days (the average month length in a 400-year Gregorian cycle). The year/month/day decomposition uses a stepped algorithm: it counts complete years, then remaining months, then leftover days — handling month-length differences correctly so you don't get impossible values like "35 days in a month."
The workday estimate multiplies total days by 5/7, giving the expected number of weekdays in the span. It does not account for holidays, so treat it as a rough guide rather than an exact payroll figure. For payroll-accurate counts, check a holiday calendar for your region. This online tool is completely free to use.
Common Use Cases
Project Timelines
Calculate exact sprint lengths, milestone gaps, or contract durations between any two specific dates. This free online tool gives you the answer instantly.
Legal & Contractual
Verify notice periods (e.g., 90-day clauses), warranty durations, and statute-of-limitations windows. Use our free calculator online for quick, reliable results.
Personal Milestones
Find out exactly how many days until a wedding, anniversary, or how long ago a major event happened. Free to use online anytime.
Time Unit Reference
| Unit | Days | Weeks |
|---|---|---|
| 1 year (non-leap) | 365 | 52 + 1 day |
| 1 year (leap) | 366 | 52 + 2 days |
| 1 month (average) | 30.44 | ~4.35 |
| 1 week | 7 | 1 |
| 1 quarter | 91.31 | ~13.04 |
| 1 decade | 3,652.5 | 521.78 |
Average month = 365.2425 ÷ 12 = 30.4369 days (Gregorian calendar). Workday estimate assumes 5-day work weeks with no public holidays.
Worked Example
Suppose you want to know the duration from January 15, 2023 to October 3, 2024. Using the date to date calculator:
- Total days: 627 days
- Total weeks: 89 weeks + 4 days
- Approx. months: 20 months
- Decomposition: 1 year, 8 months, 18 days
- Workdays (est.): ~448 days
The year/month/day result is not the same as dividing 627 by 365 or 30 — because months vary in length. The stepped algorithm is more intuitive for human-readable durations.
Why Total Months Differs from the Month Component
The date to date calculator shows two "month" numbers that look different. The approximate total months is a simple ratio: total days ÷ 30.4375. For 627 days, that gives ~20 months.
The month component in the year/month/day breakdown is the remaining months after stripping out complete years. 1 year 8 months 18 days means 1 complete year plus 8 complete months plus 18 leftover days — they measure the same span, just expressed differently.
Tips for Using This Free Online Calculator
5/7
The workday fraction used for estimates. Multiply total days by this for a rough weekday count.
30.44
Average days in a month across the Gregorian 400-year cycle — used for the approximate month count.
365.25
Average days in a year when accounting for leap years. Useful for rough year-from-days conversions.
Any Order
The date to date calculator accepts dates in any order — it always returns a positive duration.
Frequently Asked Questions
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