School-start age: an age calculation is not an admissions decision
A child may have reached an age today but not have reached it on the assessment date. The useful question is “How old on that specific date?”, followed by a comparison with the school’s written rule.
Start with the applicable written rule
You need the birth date, the institution’s age-assessment date and its minimum age. A calculator compares those inputs; it does not establish admission or entitlement to enrol.
UK guidance, for example, distinguishes school starting age from compulsory school age within its own jurisdiction. This illustrates why the relevant authority matters; it is not a rule to apply to schools elsewhere.
References: GOV.UK — School starting age: an example of jurisdiction-specific guidance
Years of age are not days divided by 365
An age threshold concerns reaching the relevant birthday in the intended calendar. Dividing days by 365 can drift because of leap years and cannot replace the institution’s age-counting rule.
Early-entry flexibility is not automatic. Enter an allowance only when the school actually permits it, using the same unit and assessment date as its stated rule.
References: US Naval Observatory — Leap years
Check the calendar on the birth record
Do not copy the numbers of a Hijri date into a Gregorian field. Confirm the accepted equivalent date on the record required for enrolment. A Civil/tabular Hijri conversion is not certification of agreement with Umm al-Qura or lunar observation.
A tabulated Islamic calendar approximates the lunar cycle. A helpful calendar conversion therefore remains distinct from validating an official document or establishing eligibility.
References: US Naval Observatory — Introduction to calendars
An illustrative rule, not official admissions guidance
Suppose an institution requires age 6 on 2026-09-01 and the child was born on 2020-09-10. The sixth birthday is 2026-09-10, 9 days after the assessment date. The strict six-year rule entered in this example is not met.
If that same institution explicitly allows entry up to 10 days early under this rule, the calculated qualifying date moves to 2026-08-31 and the comparison is met on 1 September. The assumed rule changed; the birthday did not, and the calculator did not issue an admissions decision.