Age Calculation Formulas
Comprehensive formulas for calculating age, time differences, and calendar-based computations
Basic Age Calculation Formulas
Simple Age Formula
This basic formula gives approximate age but doesn't account for birthday timing
Exact Age Calculation
If birthday has occurred this year:
If birthday hasn't occurred this year:
Conditional Age Formula
Where birthday status is determined by comparing current date with birth date
Precise Time Difference Formulas
Days Between Dates
Where dates are converted to Julian day numbers for calculation
Years, Months, Days
Years:
Months:
Days:
*Requires adjustment for negative values
Hour Precision
Total Hours:
With Time:
Second Precision
Total Seconds:
Where:
D = days, H = hours
M = minutes, S = seconds
Leap Year & Calendar Formulas
Leap Year Detection
Gregorian Calendar Rule:
Simplified Logic:
1. If divisible by 400 → Leap
2. Else if divisible by 100 → Not leap
3. Else if divisible by 4 → Leap
4. Else → Not leap
Days in Month Formula
Month Days Array:
February Calculation:
Advanced Age Calculation Methods
Julian Day Number Method
Most accurate method for calculating exact days between any two dates
Age in Different Units
Age in Months:
Age in Weeks:
Age in Hours:
Fractional Age
Decimal Years:
Precise Decimal:
Time Zone & Daylight Saving Adjustments
UTC Conversion
Local to UTC:
UTC Offset includes DST adjustment
Cross-timezone Age:
DST Considerations
Spring Forward:
Fall Back:
Alternative Calendar Systems
Islamic Calendar
Hijri Year:
G = Gregorian year
Lunar calendar with 354-355 days/year
Hebrew Calendar
Hebrew Year:
Approximate conversion
Lunisolar calendar with leap months
Chinese Calendar
Chinese Year:
Traditional count
Lunisolar with 60-year cycles
Age Calculation Examples
Example 1: Basic Age
Given:
• Birth: March 15, 1990
• Current: October 22, 2024
Calculation:
Years: 2024 - 1990 = 34
Birthday passed? March 15 < Oct 22 ✓
Result: 34 years, 7 months, 7 days
Example 2: Leap Year Impact
Given:
• Birth: February 29, 2000
• Current: February 28, 2024
Calculation:
Years: 2024 - 2000 = 24
Birthday passed? Feb 29 > Feb 28 ❌
Result: 23 years, 11 months, 30 days