Lunar phases (or Phases of the Moon) are the result of looking at the illuminated half of the Moon from different viewing geometries; they are not caused by shadows of the Earth -- this would be a lunar eclipse. The Moon exhibits different phases as the relative geometry of the Sun, Earth and Moon change, appearing as a full moon when the Sun and Moon are on opposite sides of the Earth, and as a new moon (also named dark moon, as it is not visible at night) when they are on the same side.

Names of lunar phases

The phases of the Moon have been given the following names, in sequential order:

Phase	Northern Hemisphere	Southern Hemisphere	Visibility
New moon	Not visible, or traditionally, the first visible crescent of the Moon
Waxing Crescent moon .	Right 1-49% visible	Left 1-49% visible	afternoon and post-dusk
First Quarter Moon	Right 50% visible	Left 50% visible	most of the day and early night
Waxing gibbous moon	Right 51-99% visible	Left 51-99% visible	afternoon and most of night
Full Moon	Fully visible	Fully visible	sunset to sunrise (all night)
Waning gibbous Moon	Left 51-99% visible	Right 51-99% visible	most of night and morning
Last Quarter Moon	Left 50% visible	Right 50% visible	late night and most of the day
Waning Crescent Moon	Left 1-49% visible	Right 1-49% visible	pre-dawn and morning
Darkened moon	Not visible	Not visible

The average calendrical month, which is 1/12 of a year, is about 30.4 days, while the Moon's phase (synodic) cycle repeats every 29.53 days. Therefore the timing of the Moon's phases shifts by an average of about one day for each successive month

Cumulus Webtag

Cumulus returns a webtag representing the current phase of the moon. One of the following eight will be returned to <#moonphase>

New moon
Waxing Crescent
First Quarter
Waxing Gibbous
Full moon
Waning Gibbous
Last Quarter
Waning Crescent