How do you handle leap day (February 29) birthdays?

We offer three policies for handling February 29 birthdays in non-leap years: ISO/European standard treats it as February 28, while US legal standard treats it as March 1. You can select your preferred policy in the calculator.

What is corrected age for premature infants?

Corrected age (also called adjusted age) accounts for prematurity by subtracting the number of weeks a baby was born before 40 weeks gestation from their chronological age. This gives a more accurate developmental age for premature babies.

How accurate is the age calculation?

Our calculations are precise to the second, accounting for leap years, varying month lengths, and time zones. We use the Temporal API for accurate date/time calculations.

Can I calculate age for a specific date?

Yes! Use the 'Calculate As Of' field to calculate age for any past or future date. This is useful for determining age on specific dates like anniversaries, legal documents, or insurance forms.

How many days old am I?

Enter your birth date in our calculator to find out exactly how many days you've lived. The calculator accounts for leap years and provides precise day counts.

What is the difference between chronological age and corrected age?

Chronological age is the time since birth, while corrected age adjusts for prematurity. For premature babies, corrected age = chronological age minus the number of weeks born early.

API Documentation

Use our REST API to calculate ages programmatically. All endpoints are free to use with reasonable rate limits.

Single Age Calculation

GET /api/age

Parameters

Parameter	Type	Required	Description
`dob`	string	Yes	Date of birth (YYYY-MM-DD format)
`asof`	string	No	Calculate age as of this date (YYYY-MM-DD). Defaults to today.
`leap_policy`	string	No	Policy for Feb 29 birthdays: 'us', 'eu', or 'iso' (default: 'iso')
`tz`	string	No	Time zone (e.g., 'America/New_York'). Defaults to UTC.
`ga_weeks`	number	No	Gestational age in weeks (24-42) for corrected age calculation

Example Request

curl "https://agecalculator.pro/api/age?dob=2000-01-15&asof=2025-09-01&leap_policy=us&tz=America/New_York"

Example Response

{
  "years": 25,
  "months": 7,
  "days": 17,
  "totalDays": 9361,
  "totalWeeks": 1337,
  "weekRemainderDays": 2,
  "hours": 224664,
  "minutes": 13479840,
  "seconds": 808790400,
  "totalMonthsInteger": 307,
  "totalMonthsFloat": 307.48,
  "nextBirthday": {
    "date": "2026-01-15",
    "inDays": 136,
    "inWeeks": 19
  },
  "legalAgeNote": null,
  "correctedAge": null,
  "paramsEcho": {
    "dob": "2000-01-15",
    "timeZone": "America/New_York",
    "asOf": "2025-09-01",
    "leapPolicy": "us"
  }
}

Bulk CSV Calculation

POST /api/age/bulk

Request Headers

Content-Type: text/csv

CSV Format

Upload a CSV file with the following columns:

dob (required): Date of birth
asof (optional): Calculate as of date
ga_weeks (optional): Gestational age
leap_policy (optional): Leap year policy
tz (optional): Time zone

Example CSV Input

dob,asof,ga_weeks,leap_policy,tz
2000-01-15,2025-09-01,,us,America/New_York
2016-02-29,2025-02-28,,eu,Europe/London
2025-07-01,2025-09-01,32,iso,UTC

Example Request

curl -X POST https://agecalculator.pro/api/age/bulk \
  -H "Content-Type: text/csv" \
  --data-binary @ages.csv

Response

Returns a CSV file with all input columns plus calculated age fields.

Error Responses

400 Bad Request

Invalid parameters or missing required fields

{
  "error": {
    "fieldErrors": {
      "dob": ["Date of birth is required"]
    }
  }
}

500 Internal Server Error

Server error during calculation

{
  "error": "Failed to calculate age",
  "details": "Error message"
}

Rate Limits

100 requests per minute per IP address
1000 requests per hour per IP address
10,000 requests per day per IP address
Bulk CSV limited to 1000 rows per request

For higher limits, please contact us for enterprise access.

Code Examples

JavaScript/Node.js

const response = await fetch('https://agecalculator.pro/api/age?' + 
  new URLSearchParams({
    dob: '2000-01-15',
    asof: '2025-09-01',
    leap_policy: 'us',
    tz: 'America/New_York'
  })
);

const data = await response.json();
console.log(`Age: ${data.years} years, ${data.months} months, ${data.days} days`);

Python

import requests

params = {
    'dob': '2000-01-15',
    'asof': '2025-09-01',
    'leap_policy': 'us',
    'tz': 'America/New_York'
}

response = requests.get('https://agecalculator.pro/api/age', params=params)
data = response.json()

print(f"Age: {data['years']} years, {data['months']} months, {data['days']} days")

API Documentation

Use our REST API to calculate ages programmatically. All endpoints are free to use with reasonable rate limits.

Single Age Calculation

GET /api/age

Parameters

Parameter	Type	Required	Description
`dob`	string	Yes	Date of birth (YYYY-MM-DD format)
`asof`	string	No	Calculate age as of this date (YYYY-MM-DD). Defaults to today.
`leap_policy`	string	No	Policy for Feb 29 birthdays: 'us', 'eu', or 'iso' (default: 'iso')
`tz`	string	No	Time zone (e.g., 'America/New_York'). Defaults to UTC.
`ga_weeks`	number	No	Gestational age in weeks (24-42) for corrected age calculation

Example Request

curl "https://agecalculator.pro/api/age?dob=2000-01-15&asof=2025-09-01&leap_policy=us&tz=America/New_York"

Example Response

{
  "years": 25,
  "months": 7,
  "days": 17,
  "totalDays": 9361,
  "totalWeeks": 1337,
  "weekRemainderDays": 2,
  "hours": 224664,
  "minutes": 13479840,
  "seconds": 808790400,
  "totalMonthsInteger": 307,
  "totalMonthsFloat": 307.48,
  "nextBirthday": {
    "date": "2026-01-15",
    "inDays": 136,
    "inWeeks": 19
  },
  "legalAgeNote": null,
  "correctedAge": null,
  "paramsEcho": {
    "dob": "2000-01-15",
    "timeZone": "America/New_York",
    "asOf": "2025-09-01",
    "leapPolicy": "us"
  }
}

Bulk CSV Calculation

POST /api/age/bulk

Request Headers

Content-Type: text/csv

CSV Format

Upload a CSV file with the following columns:

dob (required): Date of birth
asof (optional): Calculate as of date
ga_weeks (optional): Gestational age
leap_policy (optional): Leap year policy
tz (optional): Time zone

Example CSV Input

dob,asof,ga_weeks,leap_policy,tz
2000-01-15,2025-09-01,,us,America/New_York
2016-02-29,2025-02-28,,eu,Europe/London
2025-07-01,2025-09-01,32,iso,UTC

Example Request

curl -X POST https://agecalculator.pro/api/age/bulk \
  -H "Content-Type: text/csv" \
  --data-binary @ages.csv

Response

Returns a CSV file with all input columns plus calculated age fields.

Error Responses

400 Bad Request

Invalid parameters or missing required fields

{
  "error": {
    "fieldErrors": {
      "dob": ["Date of birth is required"]
    }
  }
}

500 Internal Server Error

Server error during calculation

{
  "error": "Failed to calculate age",
  "details": "Error message"
}

Rate Limits

100 requests per minute per IP address
1000 requests per hour per IP address
10,000 requests per day per IP address
Bulk CSV limited to 1000 rows per request

For higher limits, please contact us for enterprise access.

Code Examples

JavaScript/Node.js

const response = await fetch('https://agecalculator.pro/api/age?' + 
  new URLSearchParams({
    dob: '2000-01-15',
    asof: '2025-09-01',
    leap_policy: 'us',
    tz: 'America/New_York'
  })
);

const data = await response.json();
console.log(`Age: ${data.years} years, ${data.months} months, ${data.days} days`);

Python

import requests

params = {
    'dob': '2000-01-15',
    'asof': '2025-09-01',
    'leap_policy': 'us',
    'tz': 'America/New_York'
}

response = requests.get('https://agecalculator.pro/api/age', params=params)
data = response.json()

print(f"Age: {data['years']} years, {data['months']} months, {data['days']} days")