Summer Solstice (June 20 or 21) - longest sunlight day of the year and shortest night - Earth's North Pole is tilted toward the Sun and the Sun reaches its highest point in the sky.

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Winter Solstice (December 20 or 21) - shortest amount of sunlight day of the year and the longest night - Earth's North Pole is tilted farthest from the Sun.

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One Synodic (phases of the Moon) Month is determined by the Moon's passage once around the Earth and is about 29 days

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The meridian is the (imaginary) great circle (on the celestial sphere) passing through the celestial poles as well as the zenith (highest location directly above the observer) and nadir (180 degrees opposite zenith) of the observer's location. It contains the north and south points on the horizon, and is perpendicular to the celestial equator and horizon.

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