Moon Phase & Next Full Moon Calculator
See the current calculated moon phase, illumination and local countdowns to the next full and new moon from one explicit UTC offset. Inputs stay in your browser.
At the entered instant the calculated phase is waxing gibbous with 87.2% illumination.
Context matters.
- Phase time is a geocentric astronomical event. Local moonrise, visibility, weather and horizon conditions are separate.
- Calculated locally with SunCalc phase geometry and CalcSpan event-search rule set 4.0.0; source reviewed 2026-08-23.
Sources & scope
The calculation guide and this source trail show what the result means, where the rule came from and when it was last reviewed. This is source-and-calculation QA, not a claim of medical, legal, tax or other professional review; time-sensitive decisions still belong with the linked authority.
A visible path from input to answer.
See the current calculated moon phase, illumination and local countdowns to the next full and new moon from one explicit UTC offset. The page keeps the calculation scope and its limits beside the result so the output can be checked, copied or revisited.
- Read the record. The calculator uses Date, Local time, UTC offset (hours) and Countdown focus supplied in the form.
- Apply the scope. It applies the Global geocentric lunar-phase timing — local moonrise, horizon, weather and visibility remain separate reference and the explicit date, unit and counting conventions shown in the result.
- Expose the checkpoints. Intermediate rows, warnings and timeline events stay visible; the emphasized row identifies the primary checkpoint when one exists.
At the entered instant the calculated phase is waxing gibbous with 87.2% illumination.
- Moon phaseWaxing gibbous
Calculation purpose: See the current calculated moon phase, illumination and local countdowns to the next full and new moon from one explicit UTC offset. This is a high-sensitivity reference output; the linked authority or qualified professional controls the final decision.
Calendar inputs use plain year-month-day semantics. Leap days, month ends, date-pair order and unsupported dates are checked before the result is shown.
Rule set 1.1.0 · Last reviewed 2026-08-23 · Next review due 2027-02-23. The source panel below contains the linked evidence.
What to know before using the result.
When is the next full moon?
Enter your local date, time and current UTC offset. CalcSpan finds the next geocentric full-moon event and converts it to the entered local offset.
Is the moon phase different by city?
The geocentric phase event is global, but its local clock date can differ by time zone. Moonrise, altitude, weather and visibility do depend on location.
How accurate is the phase time?
The event search uses SunCalc phase geometry and is regression-checked against U.S. Naval Observatory primary-phase times; it is not an observation or visibility forecast.