Date of Birth

Get the user’s date of birth from HealthKit

getDateOfBirth

Retrieve the user’s date of birth stored in HealthKit. This is a synchronous operation.

Signature

function getDateOfBirth(): Date | undefined

Returns

dateOfBirth · Date | undefined

The user’s date of birth as a Date object, or undefined if not set

Example

import { getDateOfBirth } from '@kingstinct/react-native-healthkit'

const dateOfBirth = getDateOfBirth()

if (dateOfBirth) {
  const age = Math.floor(
    (Date.now() - dateOfBirth.getTime()) / (365.25 * 24 * 60 * 60 * 1000)
  )
  console.log(`Date of birth: ${dateOfBirth.toLocaleDateString()}`)
  console.log(`Age: ${age} years`)
} else {
  console.log('Date of birth not set')
}

---

getDateOfBirthAsync

Asynchronous version of getDateOfBirth. Use this if you need to await the result or want consistency with other async HealthKit operations.

Signature

function getDateOfBirthAsync(): Promise<Date | undefined>

Returns

dateOfBirth · Promise<Date | undefined>

Promise that resolves to the date of birth or undefined

Example

import { getDateOfBirthAsync } from '@kingstinct/react-native-healthkit'

const dateOfBirth = await getDateOfBirthAsync()

if (dateOfBirth) {
  const today = new Date()
  const birthDate = new Date(dateOfBirth)
  
  let age = today.getFullYear() - birthDate.getFullYear()
  const monthDiff = today.getMonth() - birthDate.getMonth()
  
  if (monthDiff < 0 || (monthDiff === 0 && today.getDate() < birthDate.getDate())) {
    age--
  }
  
  console.log('User age:', age)
  
  // Check if user is adult
  if (age >= 18) {
    console.log('User is an adult')
  } else {
    console.log('User is a minor')
  }
} else {
  console.log('Date of birth not available')
}

Example: Calculate Age in Months for Infants

import { getDateOfBirthAsync } from '@kingstinct/react-native-healthkit'

const dateOfBirth = await getDateOfBirthAsync()

if (dateOfBirth) {
  const ageInMonths = Math.floor(
    (Date.now() - dateOfBirth.getTime()) / (30.44 * 24 * 60 * 60 * 1000)
  )
  
  if (ageInMonths < 24) {
    console.log(`Infant age: ${ageInMonths} months`)
  }
}

Date of birth is a characteristic stored in the user’s HealthKit profile. It cannot be changed by apps and is set by the user in the Health app settings or Medical ID.

You need to request read authorization for characteristics before accessing this data. This is typically done during initial app setup with requestAuthorization.

Always handle the case where date of birth is undefined, as users may not have set this information in their HealthKit profile.

Date of birth is useful for age-based features, personalized health recommendations, and calculating age-adjusted metrics like VO2 max or target heart rate zones.