Moon Phase Calculator
Estimate the Moon phase, age, illumination, and upcoming quarter dates from a date, time, and UTC offset.
Enter a date, time, and UTC offset to estimate the Moon phase for that moment. The calculator stays on this page and is useful for photography plans, skywatching notes, garden journals, tide-aware reminders, and quick calendar checks.
Use the local calendar date for the place or event you are checking.
Leave the default at noon when the exact time is not important.
Use the offset active at that place and date, such as -5, 0, 1, or 5.5.
How it works
The calculator compares your selected moment with a standard reference new moon and the average length of the lunar synodic month. It reports where that moment falls in the repeating new, first-quarter, full, and last-quarter cycle.
Illumination is an estimate of the visible disc, not a weather forecast or a location-specific visibility prediction. Moonrise, moonset, altitude, clouds, terrain, and local horizon obstructions can all change what you actually see.
Use the UTC offset that applies at the selected place and date. This tool is suitable for planning and notes, but use an observatory, nautical almanac, or authoritative ephemeris for navigation, scientific observation, legal deadlines, or safety-critical work.
