What is a "conjunction" exactly?

The precise moment the Moon's ecliptic longitude relative to the Sun equals 0° — i.e., when the Moon passes between Earth and Sun and is not illuminated as seen from Earth. It's a well-defined astronomical event, distinct from a visible crescent.

How is the conjunction calculated?

Using the astronomy-engine library's SearchMoonPhase function, which finds the next moment after your chosen date where the Moon's ecliptic longitude relative to the Sun is exactly 0°.

Why is the result shown in UTC instead of my local time zone?

Conjunction is a single moment in time worldwide; showing it in UTC avoids implying a location-specific clock time, since this tool doesn't collect a location input.

How long after conjunction can the crescent actually be seen?

There's no fixed number — it depends on the Moon's angular distance from the sun, its altitude at sunset, atmospheric conditions, and the observer's location in the days following conjunction. It's typically at least a day or more, per this tool's own note, but never predicted here.

Why doesn't this tool just predict the sighting date directly?

Because actual crescent visibility depends on real-time local conditions (location, horizon, weather, the moon's elongation and altitude) that aren't fully computable from orbital mechanics alone — that's a genuinely separate question from the conjunction moment.

What's the difference between this tool and the Hijri Date Converter?

The Hijri Date Converter uses the Umm al-Qura tabular calendar (a fixed arithmetic approximation), while this tool computes the real astronomical conjunction directly with no lookup table — the two can disagree by a day, and both can differ from actual local moonsighting announcements.

Is this tool affiliated with any moonsighting committee or fiqh council?

No — it's a general astronomical calculation using the open-source astronomy-engine library, not an official position from any moonsighting committee or fiqh authority.

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Islamic Tools

Moon-Sighting (Hilal) Calculator

Next astronomical new moon (conjunction) date — not a moonsighting prediction.

🔒 Runs entirely in your browser — nothing here is ever uploaded

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Last reviewed 2026-09-06

About the Moon-Sighting (Hilal) Calculator

Shows the next real astronomical new moon (conjunction) after a given date — explicitly not a moonsighting or Islamic-month-start prediction.

100% Free Runs in Your Browser No Sign-Up Required

How to use it

Enter a starting date (defaults to today).
The tool searches forward astronomically from that date.
Read the date of the next real astronomical conjunction (new moon), shown in UTC.
Remember this is not a sighting or Islamic-month-start date — check your local moonsighting authority or this site's Hijri Date Converter for that.

Formula

Uses astronomy-engine's SearchMoonPhase to find the next moment the Moon's ecliptic longitude relative to the Sun equals 0° (exact conjunction).

Worked example

From September 6, 2026, the next conjunction falls around September 11, 2026 (UTC) — the earliest a crescent could conceivably become visible anywhere is roughly a day or more after this.

Interpreting your result

A new Islamic month traditionally begins with an actual crescent (hilal) sighting, which happens roughly a day or more AFTER conjunction and depends on the observer's location and local visibility — genuinely not computable from astronomy alone. This tool intentionally shows only the conjunction moment, not a predicted sighting date.

Recommendations

• For an actual Islamic calendar date, use this site's Hijri Date Converter (the Umm al-Qura tabular calculation) or check your local moonsighting committee's real announcement — not this tool.

Frequently asked questions

No — it shows only the astronomical conjunction moment. The actual start of a new Islamic month depends on a real moonsighting announcement (or a country's chosen tabular calendar), which this tool doesn't predict.