What is Moon's age?

The term " Moon's age " is not a reference to how long the Moon has existed (about 4.5 billion years, if you're wondering), but rather how many days it's been since the last new Moon.

What happens if the Moon is less than 50% illuminated?

This is the phase where the moon is less than 50% illuminated but has not yet reached 0% illumination (which would be a New Moon). In this part of the moon cycle, it is getting closer and closer to the Sun as viewed from Earth and the night side of the Moon is facing earth with a decreasingly thin crescent being illuminated.

What does 0 mean on a new moon?

This tells us the amount of days since the previous new Moon, or in other words, how many days into the lunar cycle we are—aka, the Moon's age. So, at the new Moon, that day is “0” (not labeled); the next day, 1 day has passed; and onward until 29 days pass and we are at the next new Moon.

Why do the arrows indicate the Moon's current position?

As the Moon's position varies from one revolution to the next, the arrow indicating the expected lunar path may not point exactly towards the Moon's current position. The arrows displayed after the Illumination, Distance, and Latitude values indicate their downward or upward trend. Note: This is a beta service.