What makes a year on earth?

Answer 1

A year is the time for the earth to orbit around the sun. About 365.25 days, and thus every 4 years an extra day is added.

Days are created by the earth spinning about its axis.

Due to the axial tilt, there is a progression of the seasons. If the southern part of the earth faces the sun, then it will be summer in the south, winter in the north, and the opposite when the northern part faces the sun.

There are a couple of different types of years depending on the reference points, and accuracy of the calculations.

The Julian year accounts for the year and leap years.

The Tropical Year is more accurate, and is the reason for the complex rules for calculating leap year days every century. It is based on the procession of the earth's axial tilt around the sun.

The Sidereal year uses the stars for reference rather than the procession of the earth's axial tilt. And, the difference between the Tropical year and the Sidereal year accounts for the procession of the equinoxes.

See Wikipedia links for Julian Year, Tropical Year, and Sidereal Year, as well as other year calculations.

Answer 2

A year on Earth is the time it takes for the Earth to make one complete orbit around the Sun. This takes approximately 365.25 days, which is why we have a leap year every four years to account for the extra quarter day.