Leap Year Checker

This tool is built for the moment you need a quick, accurate answer without opening a spreadsheet.

Note on errors: the most common slip-up here is a missing comma, an unclosed bracket, or a stray character carried over from a copy-paste. If that happens, double-check your input rather than the tool — the calculation itself runs the same way every time.

Your data stays private. Everything you type runs locally in your own browser tab. Nothing is uploaded, logged, or stored on a server — close the tab and it's gone.

This tool processes everything client-side, inside your browser window, using structural pattern checks against your input, comparing bracket and quote counts the same way a parser would. Year input text elements; range calculation views; historical logs Nothing is sent to a server, so there's no upload delay and no privacy trade-off.