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The lunar month is divided into eight basic phases:

– The new phase, when the Moon lies in front of the Sun   

– The waxing (increasing) crescent, growing into a thicker crescent over time   

– The first quarter, when the Moon appears as a half-circle (one week into the four week cycle)   

– The waxing gibbous phase, when the Moon swells slowly toward fullness   

– The full phase, with a round, happy face   

– The waning (diminishing) gibbous phase, when the once-full Moon diminishes   

– The last (or third) quarter, three weeks into the cycle (mirroring the first quarter phase)   

– The waning crescent phase, with a thinner crescent every day   

These phases are evenly separated throughout the 29.5 day lunar month, so each one occurs over 29.5 ÷ 8 = 3.7 days.

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If the Moon runs through all eight phases in 29.5 days, then to go from the waxing crescent phase to first quarter to waxing gibbous to full and then to waning gibbous takes the Moon through four of the eight phases, over half a lunar month, or 29.5 ÷ 2 = 14.75 days.

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