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Moon age (days)
Find the moon phase for any date, past or future, plus how many days until the next full and new moon.
Enter any date — past, present or future — and this tool calculates what phase the moon was, or will be, in on that day: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, or waning crescent. It also shows the moon's 'age' in days since the last new moon, and how many days remain until the next full moon and new moon.
The moon completes a full cycle of phases roughly every 29.53 days, a period known as a synodic month. This tool calculates the phase by measuring how many days have elapsed since a known reference new moon date, then finding the remainder after dividing by the length of the synodic month, which places the current date at a specific point in the cycle. That position is then mapped to one of the eight named phases, along with an approximate illumination percentage.
Moon phases are used well beyond stargazing: many lunar and lunisolar calendars, including the Hijri and Chinese calendars, are built directly around new moon dates; gardeners and anglers sometimes plan activities around specific phases; photographers use full moon dates to plan shoots; and plenty of people simply like knowing what the sky looked like on a specific date, such as their birth date or a historic event.
This calculator uses a standard astronomical approximation based on the average length of the lunar cycle, which is accurate to within roughly a day for most practical purposes. For precise, second-by-second lunar timing needed in professional astronomy or navigation, dedicated ephemeris data that accounts for the moon's slightly irregular orbital speed would be needed instead.
Several calendar systems in active use today are built directly around the moon's phases rather than the sun's position — the Hijri calendar marks the start of each month at the sighting of a new crescent moon, and the traditional Chinese calendar similarly anchors its months to new moons, adjusting periodically with leap months to stay roughly aligned with the solar year. Understanding the moon phase for a given date gives useful context for why those calendars behave differently from the fixed-length months of the Gregorian calendar.
It's accurate to within about a day for any date, which is precise enough for general reference, planning, or curiosity, though it uses an averaged cycle length rather than exact orbital mechanics.
It's the number of days that have passed since the most recent new moon, ranging from 0 (new moon) up to about 29.5 (the next new moon).
Yes, the calculation works for any date, since it's based on counting elapsed days from a known reference point rather than looking up a limited table.
Because the lunar cycle (about 29.5 days) is slightly shorter than most calendar months, it's possible for two full moons to fall within the same calendar month roughly every two to three years — the second one is sometimes called a 'blue moon'.
No, it reports the named phase and an approximate illumination percentage in text form rather than a visual rendering.