Garudapurana 2.25.10

2.25.10

bālaścātha parañjñeya āmāsasaptaviṃśati /
ā pañca varṣātkaumāraḥ paugaṇḍo navahāṃyanaḥ //

thereafter he should be known as a child up to twenty-seven months; / up to five years he is in boyhood; at nine years he is an older boy;