Results
Decimal Years
Total Months / Weeks
Years & Fraction
Remaining Days
Years‑Months‑Days (Exact, calendar‑aware)
Age Today
Age on Specific Date
Next Birthday (years)
Batch Convert
Paste one number of days per line (or comma/space separated). Results table can be exported.
| # | Days | Basis | Decimal Years | Months | Weeks | Rem Days |
|---|
Examples & QA
- 365 days → 1.0000 y (365 basis), 0.9993 y (365.2425).
- 10,000 days → compare across bases quickly using the selector.
- DOB 2000‑02‑29 to 2025‑03‑01 validates leap‑year handling.
- 0 days → 0 years; negative inputs will show a friendly error.
FAQs
Which year basis should I choose: 365, 365.25, or 365.2425?
Use 365 for common‑year approximations, 365.25 for Julian average, and 365.2425 for Gregorian average. For exact, calendar‑aware age, switch to DOB/Date mode and choose “Actual”.
Why do decimal years differ from Years‑Months‑Days?
Decimal years use a constant divisor (e.g., 365.2425), while calendar Y‑M‑D counts real months and leap days. They rarely match exactly—both are valid for different purposes.
How do leap years affect results?
Only “Actual” (calendar‑aware) uses true date math that includes leap days. Constant‑basis conversions divide by a fixed average year length and ignore the specific leap‑day pattern.
Can I calculate “age on a specific date” or “next birthday”?
Yes—use DOB/Date mode and fill the “Specific Date” field. The tool will also show the next birthday in years based on your birth date.
Is my data stored?
No. Everything runs in your browser. You can share your settings safely using the “Copy Shareable URL” button which encodes state in the address bar.