What Is a Leap Year?
A leap year is a year with 366 days instead of 365. The extra day is added to February, making it 29 days long instead of 28. Leap years help keep the calendar aligned with the Earth's orbit.
This matters for any date calculation that crosses February in a leap year. Even a single extra day can change the result for countdowns, ages, durations and deadlines.
That is why quality date calculators should always handle leap years automatically. If they do not, they risk returning incorrect answers for real-world date ranges.
Useful Next Step
After reading this guide, many users want to try the relevant calculator immediately. That is why the guide pages on DaysDifference.com are linked directly to matching tools. This helps users move from explanation to action without friction.