Date of Birth

Date of Birth is a current Health profile characteristic. Apps read it with permission through HKHealthStore.dateOfBirthComponents(), which returns Gregorian calendar date components. Third-party apps cannot write the characteristic.

The identifier has existed since iOS 8. The date-components getter arrived in iOS 10 and replaced the older dateOfBirth() getter, which is deprecated. Neither getter returns a stream of dated HealthKit samples.

A birth date identifies a calendar day, rather than the instant someone was born. Converting it to midnight in one time zone and displaying the instant in another can move the visible date to the previous or following day. Preserve the year, month and day when exchanging or displaying the value.

A simple subtraction of birth year from measurement year can overstate age before the birthday. An age computed today is also not the age at a workout or health measurement years earlier.

Apple documents an unavailable result when the user has not entered a birth date or has denied read access. The result alone does not identify which explanation applies. Handle getter errors separately, and avoid substituting a guessed birth date or age.

PulsHealth stores an optional current birth-date field supplied through app profile settings. It is separate from syncing HealthKit samples; its presence does not prove that the date originated from this HealthKit characteristic. It also does not supply a history of profile corrections.

The database coverage review checked availability without exporting the private birth date. A distribution, sample cadence or trend figure would not add useful evidence for a single current profile property.

Activity Move Mode has documented age-dependent behavior. Biological Sex is another current profile field. Heart Rate measurements have timestamps: any age-based interpretation should use age at the relevant measurement, while keeping the formula and its assumptions explicit.