In 46 BC Julius Caesar created the 1st leap year to correct for the fact that a year is 365 days plus 6ish hours or ¼ of a day. So every four years the calendar makers add a day. This is the year and the 29th is the day.
Viola tricolor, Johnny jump up (sorta like leaping) has been around longer than Caesar’s leap year. This dates back to Zeus! Ancient Athenians adopted this as the city’s symbol and Roman Pliny prescribed it to cure headaches.
And it still brings spring joy 2066 years after Caesar macgyvered the calendar.