# Moon Phase Visualizer: Moon Phase Tool and Watch Setting Guide
The Moon Phase Visualizer shows the current lunar phase with a realistic rendering of the moon. See illumination percentage, moon age, days until next full moon, and next new moon. Designed for watch enthusiasts who need to set their moon phase complication accurately-also works as a general lunar calendar for any date past or future.# Moon Phase Glossary
- New Moon
- The moon is between Earth and the sun. The illuminated side faces away from us. 0% illumination. The start of the lunar cycle.
- Waxing Crescent
- 1-49% illumination. A thin crescent appears on the right side (Northern Hemisphere). The moon is moving toward first quarter.
- First Quarter
- 50% illumination. Half of the visible surface is lit. The moon has completed one quarter of its cycle.
- Waxing Gibbous
- 51-99% illumination. More than half is lit. The moon is building toward full.
- Full Moon
- 100% illumination. The entire visible surface is lit. The peak of the lunar cycle.
- Waning Gibbous
- 99-51% illumination. The lit area begins to shrink from the right side.
- Last Quarter
- 50% illumination. The left half is lit. Three quarters of the cycle complete.
- Waning Crescent
- 49-1% illumination. A thin crescent on the left before the cycle resets to new moon.
# How to Set a Moon Phase Watch
- Use this tool to find today's exact moon phase. Note the phase name and visual appearance.
- On your watch, pull the crown to the moon phase setting position (usually position 2 or 3).
- Advance the crown until the moon disc shows the same phase as the tool. The full moon indicator is typically at the centre-top of the disc.
- Avoid setting the moon phase between 9 PM and 3 AM when the date-change mechanism is engaged and can be damaged.
- Most mechanical moon phase watches use a 59-tooth gear that approximates two lunar cycles (59 days). This means they gain about one day of error every 2 years.
- For high precision, some watches (Patek Philippe, A. Lange & Söhne) use gears that are accurate to within one day every 100+ years.
Never Set During Date Change
Do not set the moon phase (or date) between approximately 9 PM and 3 AM. During this window the watch's date-change mechanism is physically engaged with the date wheel. Forcing the crown can strip gear teeth. If you must set during this period, first advance the hands past 3 AM, then set the moon phase.
# Mechanical vs High-Accuracy Moon Phase
| Type | Tooth Gear | Error Accumulation | One-Day Drift After | Example Watches |
|---|---|---|---|---|
| Standard / Entry | 59 teeth | ~1 day every 2 years | ~2.5 years | Seiko, Orient, Hamilton, Tissot |
| Intermediate | 135 teeth | ~1 day every 10 years | ~10 years | Omega, Tudor, IWC, Breitling |
| High Accuracy | Gear train | ~1 day per 100+ years | 100+ years | Patek Philippe, A. Lange & Söhne |
Reading the Moon Disc
On most moon phase watches, the moon disc shows two moons opposite each other. Each full moon aligns with the centre-top aperture. After one full cycle (29.5 days), the second moon takes its place. This is why a 59-tooth gear works: it completes one full rotation in 59 days-exactly two lunar cycles.Quick Reference
The lunar (synodic) cycle is exactly 29.53058867 days. The tool uses this value for maximum accuracy.
Eight phases repeat in an eternal cycle: new → waxing crescent → first quarter → waxing gibbous → full → waning gibbous → last quarter → waning crescent.
To set a moon phase watch: find today's phase here, then match it on your watch's disc.
Never force the crown between 9 PM and 3 AM. Advance the time past 3 AM first.
Standard 59-tooth moon phases drift by about one day every 2.5 years. Correction requires advancing the disc by one click.