Developmental & early childhood · PRO-ED
DAYC-2 Age Calculator
Chronological age in total months for the Developmental Assessment of Young Children, Second Edition, with the published age range Birth – 5:11 checked for you.
DAYC-2 at a glance
| Full name | Developmental Assessment of Young Children, Second Edition |
|---|---|
| Publisher | PRO-ED |
| Published age range | Birth – 5:11 |
| Age format | Total months |
| Corrected age | Corrected age is often used for preterm children under 2 in early-intervention settings. State clearly in the report which age was used. |
| Discipline | Developmental & early childhood |
The DAYC-2 is a norm-referenced developmental measure for cognition, communication, social-emotional, physical development and adaptive behaviour, administered largely by observation and caregiver interview. It is a common Part C early-intervention eligibility tool.
How the DAYC-2 wants the age entered
Enter chronological age in total completed months. The DAYC-2 is organised by month of age across five domains, and the entry point for each domain is set from that figure.
The underlying calculation is the same for every instrument — complete years, complete months, then the leftover days. What differs is which part of it goes on the form. The calculator above reports all four figures at once, so you can copy the one the DAYC-2 manual asks for without recalculating:
- Years;months.days — the full record-form format, e.g. 1;6.20
- Years;months — complete units only, e.g. 1;6
- Complete months — e.g. 18 months
- Rounded to nearest month — e.g. 19 months (1;7), using the 15-day threshold
The exact date arithmetic, including month-end clamping and leap-day handling, is documented in the calculation methodology.
Worked example
A child born February 26, 2025 and assessed on September 15, 2026:
- Chronological age: 1 year, 6 months, 20 days
- Record on the DAYC-2 as: 18 months
- Day remainder: 20 days — 15 or more, so a nearest-month rounding rounds up
Enter these exact dates above to reproduce the result. Every figure on this page is computed by the same library that runs the calculator, so the worked example and the tool can never disagree.
Corrected age and the DAYC-2
Corrected age is often used for preterm children under 2 in early-intervention settings. State clearly in the report which age was used.
Corrected (adjusted) age is measured from the due date rather than the birth date. Switch the calculator above to Born preterm and enter the gestational age at birth to see both figures side by side. The dedicated adjusted age calculator adds gestational and postmenstrual age, and the corrected age guide explains the convention for families.
Other instruments
Same calculation, different recording format. These are the instruments most often administered alongside the DAYC-2:
| Instrument | Age range | Age format |
|---|---|---|
| Bayley-4 | 16 days – 42 months | Years;months.days |
| Mullen | Birth – 68 months | Years;months.days |
| BDI-3 | Birth – 7:11 | Total months |
| ASQ-3 | 1 – 66 months | Total months |
| ASQ:SE-2 | 1 – 72 months | Total months |
| Denver II | Birth – 6:0 | Years;months.days |
The full list is on the assessment instrument reference, and the assessment age calculator covers any instrument not listed individually.
DAYC-2, PRO-ED are trademarks of their respective owners. AgeCalc is not affiliated with, endorsed by, or sponsored by any of them. Brand names are used descriptively to identify the assessment formats this calculator supports.