Last updated: September 12, 2025
Multi-person, leap-year-aware, exportable results.
Mode
Switch between comparing many people or a simple two-date difference.
People / Dates
Minimum 2 rows • Soft cap 20
Options
Results
| Pair | Older → Younger | Y / M / D | Days | Weeks | Hours | Minutes |
|---|
How it’s calculated
Method notes
- Dates are normalized as UTC-only (e.g.,
Date.UTC(y, m-1, d)) to avoid timezone/DST skew. - Year/Month/Day differences are computed by borrowing months/days when needed to match calendar arithmetic.
- Total days are computed from UTC midnight to UTC midnight; toggle inclusive to include both endpoints.
- Leap years follow Gregorian rules (divisible by 4, except 100 unless also 400).
References
- MDN: Date.UTC() and UTC methods
- ECMA-262: JavaScript Date specification
- timeanddate.com: Gregorian leap year rules
This Age Difference Calculator lets you compare two or more people at once, shows Years/Months/Days and Total Days, supports an inclusive day-count option, and gives you CSV/Copy actions for instant sharing. The math is UTC-normalized (no timezone quirks) and even handles leap years properly. Compute, sort, export—done.
Why This Calculator Stands Out
- Multi-person, pairwise comparison
Add multiple rows; the tool computes all pairwise gaps and shows a sortable results table so you can spot the smallest or largest differences quickly. - Exact outputs you can trust
See Y/M/D and Total Days by default; toggle Weeks/Hours/Minutes on demand. - Inclusive day-count (optional)
Need to count both start and end days (e.g., ceremonial or admin contexts)? Flip a simple checkbox. The engine adds one day when inclusive mode is on. - One-click sharing
Export CSV, Copy Summary, or Print/Save PDF right from the action bar. - Next birthdays at a glance
See who’s celebrating next and in how many days—auto-computed from each DOB (handles Feb-29 birthdays gracefully). - Mobile-first, print-friendly UI
Clean inputs, custom radios/checkboxes, responsive grid, and a tidy print stylesheet for crisp PDFs.
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Quick Start (3 steps)
Choose Mode:
Multi-person (pairwise) for groups.
Between two dates for a classic two-date difference.
- Enter data:
Add a Name and Day/Month/Year for each row. Keep adding rows as needed and press Compute. - Refine & share:
Click table headers to sort, toggle extra units, switch Inclusive on/off, and use the CSV/Copy/PDF buttons to share.
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How the Calculation Works (Transparency = Trust)
- UTC-normalized dates
Every date is normalized to UTC before math begins—so no DST/timezone surprises. - Calendar-true Y/M/D
The Y/M/D difference utilizes standard calendar notation (month/day) for accurate, human-readable gaps. - Total Days (exclusive vs inclusive)
Midnight-to-midnight difference with an inclusive switch to add one day when your context requires counting both endpoints. - All pairwise combinations
The engine generates every unique pair automatically for you—perfect for classes, squads, or invite lists. - Next Birthday logic
Computed from today’s UTC date; Feb-29 birthdays map to Mar-1 on non-leap years (common civil approach).
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Step-by-Step Example (Relationship or Friends Group)
Choose Multi-person (pairwise).
Add Alice (1992-04-03), Ben (1990-11-12), Chloe (1995-02-28), and Dan (1989-07-05).
Keep Y/M/D and Days on; optionally enable weeks, hours, and minutes.
- Decide whether your context needs Inclusive day counting; if yes, tick the checkbox.
- Hit Compute → Sort by Days to see smallest/largest gaps; click Export CSV for email or Sheets.
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Frequently Asked Questions (FAQs)
We normalize all dates to UTC and use calendar-true Y/M/D math with month/day borrowing. Total Days uses midnight-to-midnight; the Inclusive toggle adds one day when needed.
Yes. Add multiple rows and the app generates all pairwise gaps automatically; then sort and export.
Yes—standard Gregorian rules, with Feb-29 next-birthday behavior mapped sensibly on non-leap years.
Use Export CSV, Copy Summary, or Print to save a clean PDF.
