Leap Year Checker
Calculate date and time values locally with visible assumptions and copy-ready results.
Use calendar math with the assumption visible
Use it for date validation, payroll rules, calendar generation, birthdays on February 29, and explaining why some years have 366 days. Leap-year rules are simple until century years appear, so the page includes the divisible-by-400 exception.
A year is a leap year if divisible by 4, except century years must also be divisible by 400. That makes 2000 leap, 2100 not leap, and 2028 leap. The examples around 2000, 2100, and 2028 are the edge cases that catch most informal explanations.
Limits and local processing
The rule applies to the Gregorian calendar, which is the modern civil calendar used by this site. The year is checked locally with a small arithmetic rule. Use the Gregorian rule only for modern civil-calendar dates. The next-years list is included so calendar builders can test more than one edge case at a glance. The rule is shown plainly.
Frequently Asked Questions
How does the leap year checker work?
A year is a leap year if divisible by 4, except century years must also be divisible by 400. That makes 2000 leap, 2100 not leap, and 2028 leap.
When should I use this tool?
Use it for date validation, payroll rules, calendar generation, birthdays on February 29, and explaining why some years have 366 days.
What should I watch out for?
The rule applies to the Gregorian calendar, which is the modern civil calendar used by this site.
Is this date tool private?
Yes. It runs entirely in your browser, so dates, schedules, and notes are not uploaded or stored.
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