A year is the time it takes the earth to go around the sun, and a day is the time it takes the earth to rotate once on its axis. The earth now rotates 3651/4 times during each trip around the sun.
But by studying the remains of plants and animals that lived millions of years ago, scientists have discovered that the year wasn’t always 3651/4 days long.
At one time, the earth rotated faster than it does today, and therefore spun around more than 3651/4 times in a year. About 85 million years ago, there were probably 370 days in a year. And 600 million years ago, the year was perhaps 425 days long!