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

The waxing moon.

At 15:19:48 UT Wednesday 20 January 2021
the moon’s phase is

WAXING CRESCENT (47.67% full)


Some factors that go into this equation:

Universal Time is 15.3466666666667 in decimal hours.
The Julian date is 2459234.97668033.
The sun’s ecliptic longitude is 300.806259467468 degrees.
Its mean anomaly is 17.4631112194 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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