What is the chronological age formula?

Chronological age equals assessment date minus birth date, normalized into years, months, and days.

When do I borrow days and months?

Borrow days when day difference is negative, and borrow months when month difference is negative.

Is this formula valid for leap years?

Yes, as long as date arithmetic uses real month lengths and leap-year dates correctly.

Chronological Age Formula

The formula is straightforward, but the borrowing rules are where errors happen. Use this reference when you need an exact, auditable result.

Base Formula

Chronological Age = Assessment Date − Birth Date

Compute year, month, and day components separately, then normalize by borrowing when day or month results are negative.

Borrowing Rules

If day difference is negative, subtract one month and add the previous month's day count.
If month difference is negative, subtract one year and add 12 months.
Keep the final order as Years, Months, Days.

Why This Matters

Standardized assessments and eligibility decisions often depend on precise age boundaries. A one-day error can place a person in the wrong scoring band.

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