The lunar calendar follows the rhythm of the Moon as it moves through its roughly 29.5-day cycle of phases, from new moon to full moon and back again. Almost every culture has tracked this cycle to organise planting, festivals, fasting, fishing and ritual, and many traditional calendars are still lunar or lunisolar today. The eight named phases — new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter and waning crescent — describe how much of the Moon’s face is lit as seen from Earth.

This tool takes a starting date and a number of days and computes the phase and illuminated percentage for each day using a transparent astronomical approximation. The illumination percentage tells you how much of the visible disc is sunlit, peaking at 100% on the full moon and dropping toward 0% at the new moon. The chart plots that curve with a small Moon icon for every day, making it easy to see at a glance when the bright nights and dark nights fall within your chosen window.

People use a view like this to plan stargazing and astrophotography, to follow gardening and fishing traditions tied to the Moon, or simply to satisfy curiosity about the night sky. The values are a close approximation suitable for everyday planning rather than precise astronomical work, and local time zones can shift a phase boundary by up to a day. Use it as a friendly guide to the lunar month and pair it with a dedicated ephemeris when exact timing matters.