About

Standard calendar math is often deceptive due to the irregularities of the Gregorian calendar system - leap years, variable month lengths (28, 30, or 31 days), and historical adjustments. This tool provides a rigorous calculation of the duration between two specific points in time.

It is designed for precision, calculating not just the number of years, but the exact count of days, hours, and minutes. This level of detail is useful for legal age verification, historical research, calculating tenure, or satisfying curiosity about the exact age gap between siblings, partners, or historical figures.

Formulas

The difference Δt is calculated by converting both timestamps to UTC milliseconds, subtracting them, and then converting back to human-readable units.

Δt = |t₂ − t₁|

Reference Data

Time Unit	Avg. Length	Notes
Year	365.2425 days	Gregorian average accounting for leap years.
Month	30.44 days	Average over 400-year cycle.
Day	24 hours	Standard solar day.

Frequently Asked Questions

Yes. The underlying algorithm utilizes the native Date object methods which account for Leap Years (every 4 years, except divisible by 100 unless divisible by 400).

No. The calculator uses the absolute difference, so it will always return a positive duration regardless of whether Date 1 is before or after Date 2.