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The waning moon.

At 20:58:24 UT Thursday 17 August 2017
the waning moon’s phase is

19.58% full

Time Zone:   

Some factors that go into this equation:

Universal Time is 20.99 in decimal hours.
The Julian date is 2457982.6957993.
The sun’s ecliptic longitude is 145.110511523138 degrees.
Its mean anomaly is 223.6643850476 degrees.
The moon’s true longitude is 92.5845157449956 degrees.

These calculations incorporate the switch to the English New Style (N.S.)—i.e., Gregorian— calendar after Wednesday, 02 September 1752; the next day became Thursday, 14 September, skipping eleven days. (Please also note that, while fairly accurate, these calculations remain a bit buggy.)

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