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 17:23:52 UT Tuesday 18 May 2021
the moon’s phase is

WAXING CRESCENT (38.94% full)

Some factors that go into this equation:

Universal Time is 17.4144444444444 in decimal hours.
The Julian date is 2459352.88944572.
The sun’s ecliptic longitude is 58.003874980599 degrees.
Its mean anomaly is 133.8544200939 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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