About this tool
Compute the duration between two dates as days, with weeks/months/years derived from average lengths.
Formula
days = round((end − start) / 86,400,000 ms). Weeks = days/7. Months ≈ days/30.4375. Years ≈ days/365.25.
Worked example
2026-01-01 to 2026-12-31 → 364 days, 52 weeks, ~12 months, ~1 year.
Notes
Months and years are average-based and not exact calendar counts. For exact age, use the Age Calculator.