External
A person is under 16 years of age when they have not yet attained their 16 — th birthday. They should be regarded as 16 on and from the date of their 16 — th birthday.
A person is under 25 years of age when they have not yet attained their 25 — th birthday. They should be regarded as 25 on and from the date of their 25 — th birthday.
Note, however, that if a period is to be calculated from a particular day or event (e.g. the child's 16 — th birthday), the time is to be reckoned exclusive of that day or the day of the event.