Leap Year Calculator
Check if any year is a leap year (366 days) and review calendar rules.
leap year-calculator Inputs
About Leap Year Calculator
The Leap Year Calculator & Century Checker determines whether any Gregorian calendar year (past, present, or future) is a leap year (366 days) or common year (365 days) based on astronomical Gregorian calendar division rules with mathematical proofs.
How to Use Leap Year Calculator
Step 1
Enter any calendar year (e.g. 2028, 2032, 2100).
Step 2
Inspect the Leap Year status badge (Yes / No).
Step 3
Review the mathematical divisibility proof and February calendar breakdown.
Practical Use Cases for Leap Year Calculator
Software Date Logic & Calendar QA
Test edge-case date handling algorithms around February 29th and century leap years (e.g. 1900 vs 2000 vs 2100).
Astronomical & Calendar Science Education
Learn the 4-year, 100-year, and 400-year leap year mathematical criteria introduced in the 1582 Gregorian reform.
Input & Output Examples
Checking Year 2028 and Year 2100
Year: 2028 and Year: 2100
2028: Leap Year (Divisible by 4) | 2100: Common Year (Divisible by 100 but not by 400)
Key Features & Performance
- ✓Applies strict 3-tier Gregorian leap year algorithm (Divisible by 4, except 100, unless 400).
- ✓Step-by-step mathematical proof breakdown.
- ✓Calculates total days in year (366 vs 365) and days in February (29 vs 28).
- ✓Lists next 10 and previous 10 leap years.
- ✓100% Client-Side instant calculation.
Key Terminology & Definitions
Gregorian Leap Year Rule
A year is a leap year if divisible by 4, except end-of-century years (divisible by 100) which must also be divisible by 400.
Tropical Solar Year
The astronomical time taken for Earth to orbit the Sun, approximately 365.2422 days, requiring leap days to prevent seasonal drift.