A leap year is a year which has 366 days. The extra day is the 29th February. There is a leap year every four years.
A leap year happens every 4 years and in February instead of 28 days they make it 29 days. But it's only once every 4 years
Which calendar, introduced in 46 BC, had a regular year of 365 days divided into 12 months, and a leap day added to February every four years?
