The eccentricity of an orbit is a measure of its deviation from a perfect circle. It's a unitless value that ranges from 0 (perfectly circular) to 1 (highly elliptical).

Eccentricity is not measured in Earth days.

You might be thinking of the orbital period, which is the time it takes for an object to complete one orbit around another object. The Earth's orbital period is approximately 365.25 days.

Here's why the two concepts are separate:

* Eccentricity describes the *shape* of the orbit.

* Orbital period describes the *time* it takes to complete one orbit.

Earth's Orbital Eccentricity:

Earth's orbital eccentricity is approximately 0.0167. This means its orbit is slightly elliptical, but close to circular.

Let me know if you'd like to learn more about eccentricity or orbital periods!