Calculate age

Count completed Gregorian years, clamped months, and remaining UTC calendar days between two valid dates.

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ToolAge Calculator
Input
Output
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How it works

Strict date-only values complete whole years first, then clamped calendar months, then count remaining UTC midnights. Total days separately divides the exact UTC-midnight interval by 86,400,000 milliseconds.

  • Today in UTC is used only when the reference date is empty.
  • A February 29 anniversary clamps to February 28 in a non-leap year under this page’s explicit policy.

Worked example

Calculate Age
Calculate age from a specific birthdate to a reference date
Input
											Birthdate: 1990-06-15
Reference date: 2025-03-20
Output
												Age: 34 years, 9 months, 5 days
Total days: 12,697
Total weeks: 1,813
Total hours: 304,728

Born: 1990-06-15
As of: 2025-03-20

Next birthday in 87 days (2025-06-15)

When to use this

Eligibility forms count completed years, genealogy notes compare known dates, and birthday plans find the next anniversary.

Edge cases

  • 2025-01-31 to 2025-03-01 is 0 years, 1 month, 1 day without a negative remainder.
  • 2024-02-29 uses February 28 for its anniversary in a non-leap reference year.
  • 2024-02-31 is rejected instead of rolling into March.

References