Age Calculation Formula Explained (With Examples)—The Ultimate Logic.

The Core Mathematical Formula

In its simplest algebraic form, chronological age is expressed as:

Where $T$ represents time. However, because our calendar uses irregular month lengths and leap years, we use a Conditional Logic Formula:

Exact Age Calculation (Years, Months, Days)

To calculate the "Exact Age" used by our Age Calculator, the logic follows these three steps:

• Years: Current Year - Birth Year (Adjusted by the 'Birthday Check' above).
• Months: If Current Day < Birth Day, Months = (Current Month - Birth Month) - 1.
• Days: If Current Day < Birth Day, Days = (Days in Previous Month - Birth Day) + Current Day.

This ensures that a person born on January 31st is correctly calculated as being 0 months and 28 days old on February 28th.

Leap Year Logic

Leap years add a day to the calendar every four years ($366$ days instead of $365$). Our formula accounts for this by using absolute timestamps or "Leap-Aware" date objects. This prevents the "drifting" of age results over decades of time.