Guides & tutorials
Short, jargon-free guides to working with ages — how to calculate an exact age by hand, how to express it in days, months or hours, and what people mean by chronological age. Every guide pairs with the free AgeCalc calculator, which does the arithmetic in your browser.
How to Calculate Age
The pencil-and-paper method for exact age in years, months and days: the borrowing steps, a fully worked example, leap years, February 29 birthdays, and how to calculate an age on any past or future date.
Age in Days, Months and Years
How total days, total months, weeks and hours are really counted, why multiplying years by 365 always comes up short, the 10,000-days milestone, and a worked example with every leap day shown.
What Is Chronological Age?
The plain-English definition, how chronological age differs from biological age, and the places — school cutoffs, licences, pensions, medicine — where the calendar number is the one that counts.