Some nights when we look at the moon, it is full and bright; sometimes it’s just a sliver of silver light. These changes in appearance are the phases of the moon. As the moon orbits Earth, it goes through eight different phases. The four primary phases of the moon occur one week apart, with the full moon being its most dazzling stage.
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Lunar calendar for 2021
Here are the phases of the moon for 2021, according to NASA’s SKYCAL. Times and dates are in UTC time.
Moon phases 2021 with dates New Moon First Quarter Full Moon Last Quarter January 6, 9:37 am January 13, 5:00 am January 20 9:02 pm January 28, 7:16 pm February 4, 5:37 pm February 11, 7:06 pm February 19, 6:47 pm February 27, 8:17 March 6, 1:30 am March 13, 10:21 am March 21, 2:40 pm March 28, 6:48 pm April 4, 10:02 am April 12, 2:31 am April 20, 6:59 am April 27, 3:31 am May 3, 7:50 pm 11 May, 7:00 pm May 19, 7:13 pm May 26, 11:14 am June 2, 7:24 am June 10, 10:53 am June 18, 3:54 am June 24 , 6:40 pm July 1, 9:11 pm July 10, 1:16 am July 17, 10:11 am July 24, 2:37 am July 31, 1:16 pm August 8, 1 : 50 pm August 15, 3:20 pm August 22, 12:02 pm August 30, 7:13 am September 7, 12:52 am September 13, 8:39 pm September 20, 11:55 pm September 29, 1:57 am October 6, 11:05 am October 13, 3:25 am October 20, 2:57 pm October 28, 8:05 pm November 4 , 9:15 pm November 11, 12; 46 pm November 19, 8:58 am November 27, 12:28 pm December 4, 7:43 am December 11, 1:36 am December 19, 4:36 am December 27, 2:24 am
(Image credit: NASA / JPL-Caltech)
The moon, like the Earth, is a sphere and is always half illuminated by the sun. As the moon travels around the Earth, we see more or less half illuminated. The lunar phases describe what part of the lunar disk is illuminated from our perspective.
New moon: the moon is between the Earth and the sun, and the side of the moon that faces us does not receive direct sunlight; it is illuminated only by faint sunlight reflected from Earth.
Waxing crescent: As the moon moves around the Earth, the side that we can see gradually brightens more from direct sunlight.
First quarter: The moon is 90 degrees from the sun in the sky and is half lit from our point of view. We call it the “first quarter” because the moon has traveled about a quarter of the way around the Earth since the new moon.
(Image credit: Karl Tate, SPACE.com)
Waxing gibbous: the area of illumination continues to increase. More than half the face of the moon appears to be receiving sunlight.
Full Moon: The moon is 180 degrees from the sun and is as close as possible to being fully illuminated by the sun from our perspective. The sun, Earth, and moon are aligned, but because the moon’s orbit is not exactly in the same plane as Earth’s orbit around the sun, they rarely form a perfect line. When they do, we have a lunar eclipse when the shadow of the Earth crosses the face of the moon.
Waning gibbous: More than half the face of the moon appears to be receiving sunlight, but the amount is decreasing.
Last quarter: the moon has moved another quarter of the way around the Earth, to the position of the third quarter. Sunlight now shines on the other half of the visible side of the moon.
Waning crescent: Less than half the face of the moon appears to be receiving sunlight, and the amount is decreasing.
Finally, the moon returns to its initial new moon position. Now the moon is between the earth and the sun. Usually the moon passes above or below the sun from our point of view, but occasionally it passes right in front of the sun and we get a solar eclipse.
Related: Infographic: How Moon Phases Work