The moon's phase and illumination for any date.
Whether you're an astronomy hobbyist, planning a night photo shoot around moonlight, or checking a date against a cultural or religious calendar that tracks lunar phases, this gives a quick, accurate-enough answer without needing a dedicated astronomy app.
Accurate to within roughly a day, which is standard for a lightweight astronomical approximation without a full ephemeris calculation — fine for casual planning, not precise scientific or navigational use.
Yes — pick any date, past or future, and the phase calculates the same way.
How many days have passed since the most recent new moon before your selected date — it resets to 0 at each new moon and counts up to about 29.5 before the next new moon begins the cycle again.
