Age Calculator & Chronology Guide
Measure time spans with precision. Calculate your exact age in years, months, and days, or find the time difference between any two historical dates.
Date of Birth (From)
Start date for calculation
Age at Date (To)
End date for calculation
Exact Age
Alternative Units
Total Months
0
Total Weeks
0
Total Days
0
Total Hours
0
Total Minutes
0
Total Seconds
0
Precision Tracking
Calculates age down to the second. Accounts for variable month lengths (28, 30, 31 days).
Leap Year Logic
Automatically detects Leap Years (29 days in Feb) occurring every 4 years to ensure total accuracy.
Total Units
Converts your lifespan into total weeks, hours, or minutes. Useful for 10,000 hour mastery tracking.
Chronological vs. Biological Age
Are you aging faster or slower than your birthdate suggests?
📅 Chronological Age
This is what our calculator measures. It is the exact amount of time that has passed from your birth to the current date. It is a constant, linear progression that cannot be stopped or reversed. It determines legal rights like voting, driving, and retirement.
🧬 Biological Age
This refers to how old your cells and tissues effectively are. Factors like genetics, lifestyle (diet, exercise), and stress can make your biological age higher or lower than your chronological age. A healthy 60-year-old might have the biological markers of a 45-year-old!
How Old Are You on Other Planets?
Mars
Year = 687 Days
0.0 yrs
Mercury
Year = 88 Days
0.0 yrs
Jupiter
Year = 11.86 Earth Yrs
0.0 yrs
Neptune
Year = 164.8 Earth Yrs
0.00 yrs
*Planetary years are calculated based on their orbital period around the Sun relative to Earth.
Cultural Age Systems
International Age System (Western)
This is the system used by this calculator and most of the world. A person starts at age 0 and ages up by 1 on each birthday.
Traditional East Asian Age
Historically used in China, Korea, and Vietnam. A baby is considered 1 year old at birth. Everyone ages up together on the New Year (Lunar or Solar), not on their individual birthday. This means a baby born on Dec 31st could be 2 years old the next day!
Frequently Asked Questions
Why is 1 year not exactly 365 days?
The Earth takes approximately 365.24219 days to orbit the Sun. To account for this quarter-day, we add a Leap Day (Feb 29) every 4 years. Without this, our calendar would drift by about 24 days every century, eventually flipping the seasons!
How accurate is this calculator?
This calculator is precise to the day. It uses the native JavaScript `Date` object which accounts for all Leap Years and varying month lengths in the Gregorian calendar system used globally today.
What determines legal age?
Legal age is purely chronological. Even if someone has a younger biological age, the law only recognizes the date on their birth certificate for voting, drinking, or retiring.
Do other planets have Leap Years?
Yes! For example, Mars has a year of roughly 668.6 sols (Martian days). Calendars designed for future Mars colonies often include complex leap rules to keep timekeeping accurate.