What Is the Moon Phase Calendar Calculator?
A moon phase calculator identifies lunar illumination and orbital phase for any calendar date.
How Does the Moon Phase Calendar Calculator Work?
Calculates days elapsed since a known astronomical reference new moon modulo the synodic lunar period.
Moon Phase Calendar Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
Illumination (%) = 50 × [1 - cos(2π × Cycle Fraction)]
Uses astronomical reference epochs to calculate position along the 29.530588-day synodic lunar cycle.
How to Use the Moon Phase Calendar Calculator
- Select any date on the calendar.
Step-by-Step Example Calculation
Moon Phase for Selected Date
Input Values:
targetDate:2026-10-06
Understanding Your Result
Shows lunar phase name, visible illumination percentage, moon age, and days until next Full and New Moon.
Factors That Affect the Result
- Earth-Moon-Sun orbital geometry and slight elliptical eccentricity.
When Should You Use This Calculator?
- Night sky stargazing, astrophotography planning, tidal fishing, and night hiking.
Assumptions & Limitations
- Geocentric geometric approximation accurate within standard visual astronomical tolerances.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard Mean Synodic Lunar Cycle mathematical model.