How is the moon phase calculated?

The moon waxes and wanes on a cycle of about 29.5 days. Counting the days since a reference point places today somewhere in that cycle, which gives the phase.

When is the full moon?

Step the date forward and find the day where the phase name turns to full moon.

Can it differ slightly from the real sky?

It uses an average cycle, so it can be about a day out. It is for gauging tonight's shape, not for precise observation.

Moon Phase

Name: 달 위상
Author: KarmoLab

Tonight's moon, phase name

달 위상

오늘의 달 위상을 확인합니다

THE MOON PHASE

🌑

신월 (New Moon) (5.947549%)

TMI 🌕
달의 공전과 자전 주기는 약 27.3일로 같아 항상 같은 면만 보입니다.
지구에서 달까지의 거리는 약 384,400km로 빛의 속도로 1.28초가 걸리며,
매년 지구에서 3.82cm씩 조금씩 조용히 멀어지고 있습니다.

Shows what shape the moon is tonight. The phase is computed from the date and given as a picture and a name, worked out inside your browser with no connection needed.

How to use it

Opening it calculates today straight away
Check the drawing and the name of the phase

Common questions

How is the moon phase calculated?: The moon waxes and wanes on a cycle of about 29.5 days. Counting the days since a reference point places today somewhere in that cycle, which gives the phase.
When is the full moon?: Step the date forward and find the day where the phase name turns to full moon.
Can it differ slightly from the real sky?: It uses an average cycle, so it can be about a day out. It is for gauging tonight's shape, not for precise observation.

Other tools

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