To look up the phase of the moon for any (Common Era) date,
just fill out the form below, then hit “Find Phase.”

The waning moon.

At 18:56:03 UT Saturday 23 October 2021
the moon’s phase is

WANING GIBBOUS (91.01% full)

Some factors that go into this equation:

Universal Time is 18.9508333333333 in decimal hours.
The Julian date is 2459511.41013657.
The sun’s ecliptic longitude is 210.614581984952 degrees.
Its mean anomaly is 289.649799805 degrees.
The moon’s mean longitude on 00 January 1990 was 318.351648 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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