Transform

Compute exact completed ages in years, months, or days from birthdate records

Derive current age in full completed years from birthday columns.

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Why Onfyt: Calculates true legal completed age using calendar birthday thresholds rather than flawed 365.25 day division.

Interactive Sample Data

patient_id	name	dob
1	Grace Kerubo	1995-04-12
2	Peter Njoroge	1982-11-28
3	Mercy Akinyi	2010-08-03

How this tool works

Age is a derived value, not a stored one. Healthcare systems, insurance pricing engines, school admissions platforms, and HR benefit calculations all record Date of Birth (DOB) and compute current age on demand — because a static age field becomes wrong every birthday. When preparing an analytical export such as a cohort breakdown, a risk-band classification, or an age-gate check, the DOB column must become an integer age for every row, calculated against a fixed reference date with leap-year arithmetic applied correctly. Computing age using naive arithmetic—such as dividing total elapsed days by 365 or 365.25—frequently yields incorrect results. Because leap years occur irregularly and months vary in length between 28 and 31 days, dividing by 365.25 can miscalculate a person's age by a full year on the days surrounding their birthday. DataFix calculates exact legal completed age by comparing calendar day and month components. A person born on December 15, 2000 does not turn 26 until December 15, 2026, regardless of how many leap days intervened. Evaluating completed calendar years relative to a reference date accounts for leap years without relying on thirty-day approximations.

Things that usually go wrong

Dates in non-ISO format (e.g. 15/04/1990) must be standardised first — use the Standardise Dates to ISO tool.
Future dates produce negative ages — these are flagged.

Edge cases we tested

🧪 Leap year birthday (February 29)

Handled according to standard convention (age increments on March 1 in non-leap years).

🧪 Future dates of birth (birthdays after evaluation date)

Flagged with validation warnings or output as 0.

🧪 Two-digit years ('95' vs '1995' vs '2095')

Normalized using century pivot thresholds to prevent 100-year offsets.

Frequently Asked Questions

How is age calculated?

Age is the number of complete years between the DoB and the reference date. A person born on 2000-01-01 has their birthday on 2024-01-01, giving age 24 on that exact day.