Moon Phase Calendar

In the Moon Calendar, you can see the four principal phases of the Moon. These are the new moon, first quarter, full moon, and last quarter. You can see the detailed information regarding the lunar phases below. The lunar phases gradually change over a synodic month which is about 29.53 days as the Moon’s orbital positions around Earth and Earth around the Sun shift. This is called a synodic month (lunar phases as observed from the Earth are correlated with the synodic month) and not to be confused with the sidereal month (the Moon appears to move completely around the celestial sphere once in about 27.3 days as observed from the Earth).

Moon Phase Calendar – Moon Phases Chart: New Moon, First Quarter, Full Moon, Last Quarter

The visible side of the moon is variously sunlit, depending on the position of the Moon in its orbit. Thus, this face’s sunlit portion can vary from 0% (at new moon) to 100% (at full moon). Each of the four “intermediate” lunar phases (see below) is approximately 7.4 days, with slight variation due to the Moon’s orbit’s elliptical shape.

• New Moon:  At new moon the Moon is between the Earth and the Sun, and is invisible as it presents its night side to the observer. If the alignment is exact a total solar eclipse will occur, but because the Moon’s orbital plane is inclined to the Earth’s, the solar and lunar disks do not usually coincide at new moon. The age of the Moon is reckoned in days from one new moon to the next. After a day or two, a sliver of the sunlit side becomes visible as a thin crescent (under exceptional conditions a crescent may be visible when the Moon is only about 12 hours old). From new moon until full moon the Moon is said to be waxing, as more of the sunlit side comes into view. You can see this with many phases in the Moon Phases Calendar.

• First Quarter: A week after new moon comes first quarter, when the Moon is a quarter of the way around its orbit. The phase at first quarter is also termed a ‘half moon’ — the terminator, the line marking the boundary between night and day, bisects the Moon’s disk. As the Moon continues to wax, the phase becomes gibbous, when most of the sunlit side is visible, a crescent shaped portion of the disk remaining in darkness.

• Full Moon: Full moon occurs at just under 15 days. As at new moon, Earth, Sun and Moon are again aligned, but this time the Moon is opposite the Sun in the sky; if the alignment is close enough, a total lunar eclipse occurs. A full moon looks bigger when it is near the horizon than when it is high in the sky. The size of the Moon is always the same. No one knows exactly what causes this common Moon illusion. Perhaps comparing the Moon with local objects as opposed to distant stars makes the difference psychologically.

• Last Quarter: After full moon the phases then repeat in reverse, the terminator continuing its passage across the disk, through the gibbous phase to last quarter, when the Moon enters the last quarter of its orbit at nearly 23 days old. In this half of its orbit the Moon is said to be waning. After passing through a crescent phase again, and the lunation ends with another new moon.

There are also four other lunar phase names defined with the help us using 4 words: crescent, gibbous, waxing, and waning. The word crescent refers to the phases where the moon is less than half illuminated. The word gibbous refers to phases where the moon is more than half illuminated. Waxing essentially means “growing” or expanding in illumination, and waning means “shrinking” or decreasing in illumination. Thus you can simply combine the two words to create the phase name, as follows:

• Waxing Crescent: After the new moon, the sunlit portion is increasing, but less than half, so it is waxing crescent.
• Waxing Gibbous: After the first quarter, the sunlit portion is still increasing, but now it is more than half, so it is waxing gibbous.
• Waning Gibbous: After the full moon (maximum illumination), the light continually decreases. So the waning gibbous phase occurs next.
• Waning Crescent:  Following the third quarter is the waning crescent, which wanes until the light is completely gone — a new moon.