December's total lunar eclipse is the only total eclipse of the moon of this year and in the Western Hemisphere it will begin on Dec. 21 at 12:29 a.m. EST (9:29 p.m. PST on Dec. 20) as the moon begins to enter Earth's penumbral shadow.    

Skywatchers won't notice any changes in the moon's appearance until about 45 minutes later when shading will become evident on the upper left portion of the moon's disk.   

The 72 minutes of the total lunar eclipse will be visible from North and South America, northern and western Europe, and northeast Asia, including Korea and much of Japan. Totality will also be visible from the North Island of New Zealand and Hawaii. 

lunar ecslipse chart

See Space.com for full details.