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Leap Year Rule and Neighbor Finder
List a bounded year interval with complete Gregorian leap-rule witnesses.
Center year, Neighbor radius
leap-year-neighbors.json
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How to use this tool
- Enter a center year from 0001 through 9999 and a radius from 0 through 100.
- Keep the complete requested interval inside that year domain.
- Find neighboring leap years and download all rule witnesses.
Examples
1900 is not a leap year; 2000 is a leap year under the 400-year rule.
Limitations
- At most 201 neighboring years, 128 raw units per integer field, 64 KiB complete JSON and 30 seconds.
- Uses the proleptic Gregorian 4/100/400 rules. Intervals crossing the year domain refuse rather than clipping.
- The distinct job is the complete neighboring interval and rule list. Existing ordinal-date tools already report a single year's leap status.
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