2 calculators
Reference
Constants, formulas, tables, and quick-lookup utilities.
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Understand reference numbers
Plain-English explainers paired with the calculators above.
4 min · formula
How age is actually calculated
Age looks simple — until you try to subtract two dates by hand. Here's the calendar arithmetic your age calculator runs for you.
4 min · mistakes
Leap years and your real age
If you were born on 29 February, when do you legally turn another year older? And how do leap days quietly change ages calculated in days?
5 min · examples
Age milestones to know
School cutoffs, voting, driving, retirement — the ages that change what you can do. A practical reference, not legal advice.
3 min · scenario
Calculating the age gap between two people
Sibling spacing, couple gaps, generational comparisons — how to measure the difference between two birth dates accurately.