Age Calculators: Milestones, Eligibility, and Date Math

Calendar age counts full years lived since birth date to a reference date—usually today or an event date. Approximate age ("about 30") ignores months. Medical gestational age and Korean traditional age use different rules—label which system you mean.

• Legal majority: jurisdiction-specific date
• Senior discounts: often 65+ on day of
• Youth sports: age as of season cutoff (Aug 1)
• Retirement accounts: IRS rules with exact dates

Born Feb 29? Some systems store Feb 28 or Mar 1 in non-leap years for anniversaries. Age in full years still advances on Mar 1 in many legal contexts—but verify locally. Date libraries handle leap days; manual day-counting often does not.

Remote hires across time zones: define whether "birth date" is local civil date or UTC instant. Forms storing only year invite age drift mid-year. Collect full ISO dates (YYYY-MM-DD) without ambiguous formats like 03/04/05.

Counting on fingers for "how old will I be on contract end date" fails across month boundaries. A calculator returns years, months, days, and total days between dates.

The Age Calculator on XSular Tools computes exact intervals in the browser—paste birth date and event date when verifying school enrollment or warranty eligibility.

• Birthday is today
• Birthday tomorrow (not yet new age)
• End of month spans (Jan 31 → Feb 28)
• Same month/day, different year
• Historical dates before 1900 (library limits)