📅Date & Time

Exact Age Calculation

Patterns for calculating age based on birthdate and current date.

Explanation

Calculating age requires handling leap years and comparing the current month/day to the birth month/day.

Examples

Born 1990

Output

34 years

Infant

Output

6 months, 12 days

Code Examples

JavaScript

function calculateAge(birthday) {
  const ageDifMs = Date.now() - birthday.getTime();
  const ageDate = new Date(ageDifMs);
  return Math.abs(ageDate.getUTCFullYear() - 1970);
}

💡 Tips

Check if the birthday has already occurred this year
Handle February 29th for leap-year babies
For small ages, use months or weeks

⚠️ Common Pitfalls

Simple year subtraction is often off by 1
Timezone changes on birth day can be tricky