How to use leap year checker
- Paste text into the editor. Inputs are limited to one million characters.
- Choose an operation where available, then run the tool.
- Review the result, copy it or save a text file.
A simple example
2000 is a leap year. 1900 is not because century years must also be divisible by 400.
What to keep in mind
Years 1–9999 using the proleptic Gregorian calendar. This does not model the dates when individual countries adopted that calendar.
Good questions. Clear answers.
Does my text leave the device?
No. This tool processes text in your browser and does not retain it.
Can I undo a change?
Your original input stays in the input editor. The result appears separately.