FizzyTools
Chronological age calculator
Age on the test date in years;months;days, with the counting your test manual uses. Free, and nothing leaves your device.
How it works
- 1Type the test dateToday, or any past or future test day.
- 2Type the date of birthAny common format, or pick it from the calendar.
- 3Pick the countingCalendar or 30-day months, with or without rounding, as your manual says.
How we count
A month counts once the same day number comes round again. If that day doesn't exist in a month (the 31st, or 29 February), the month counts from the month's last day. This is the rule of the international date standard used by modern browsers (Temporal) and by Java.
| Born | On | Age |
|---|---|---|
| 31 January 2026 | 28 February 2026 | 28 days |
| 31 January 2026 | 1 March 2026 | 1 month 1 day |
| 29 February 2000 | 28 February 2001 | 11 months 30 days |
| 29 February 2000 | 1 March 2001 | 1 year 1 day |
Questions
What is chronological age?
A child's exact age on the day of a test, in years;months;days (for example 6;1;23). Scores are compared with children of the same age, so the months and days matter.
Calendar months or 30-day months?
Calendar counting is exact. Many test manuals print a hand method that treats every month as 30 days when borrowing, which can give a day or two more. Use the method your test's manual gives.
Should I round the days?
Some manuals drop the days, others round 15 days or more up to the next month. Pick the rounding your manual asks for; the total months follow it.
Can I work out the age on a past test date?
Yes. Type any test date; it doesn't have to be today.
Can I do a whole class at once?
Yes. Open List, paste names and dates of birth, and set "Age on" to the test date.
Is any child's data saved or sent?
No. Everything is worked out in your browser and nothing is saved.