Understanding the Common Night Criterion
THE QUR’ANIC BASIS FOR THE START OF THE MONTH IN THE ISLAMIC CALENDAR
Determination of the start of a lunar month is based on two ayahs in the Quran: 2:185 and 2:189.
In Ayah 2:185, interpretations of “shahida” range from the literal understanding of seeing with one’s physical eyes to broader understandings of knowing through inference or other forms of ascertainment. Ayah 2:189 provides the lunar basis for the Islamic calendar.
“…فَمَن شَهِدَ مِنكُمُ الشَّهْرَ فَلْيَصُمْهُ…
…so whoever from you witnesses the month, so he shall fast it…”
“يَسْأَلُونَكَ عَنِ الْأَهِلَّةِ قُلْ هِيَ مَوَاقِيتُ لِلنَّاسِ وَالْحَجِّ
They ask you about the crescent moons; say ‘They are demarcations of time for the people and the Hajj…”
DECISION POINTS IN ASCERTAINING THE NEW LUNAR MONTH
Based on the Quranic verses, there are several methods to ascertain the beginning of a lunar month. These methods are generally distinguished by two decision points.
The first decision point is how the crescent moon is “witnessed.” The moon may be sighted physically, or if 30 days have passed since the beginning of the lunar month without a sighting, the next day must be the start of the new month because lunar months are always 29 or 30 days. In addition, the presence of the new moon may be calculated according to various parameters (knowledge without sighting).
If the moon must be sighted physically, then the second decision point is whether one can see the moon him/herself. If not, then one may accept the sighting of another trustworthy competent person. However, the third decision point is how far away another person may be to accept his/her sighting of the moon.
There are two main opinions on this matter: the Common Horizon criterion and the Common Night criterion.
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This is the more local criterion, defined as follows:
“If the first day of a month is proved in a city, it is also proved in other cities if they are united in their horizon. And the meaning of having a common horizon in this matter is that if new moon was sighted in a city, there would be a distinct possibility of sighting it in the other cities, if there were no impediments, like, the clouds etc.” [Source]
In other words, if it is astronomically possible to see the moon in locations A and B, but the sighting is obscured in location A, the Common Horizon criterion says individuals living in location A can accept the sighting of location B. The Common Horizon criterion stipulates that the moon should appear similarly in both locations with respect to its altitude above the horizon and degree of illumination; hence, the horizons of the two locations are similar.
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This broader criterion is defined as follows:
“If the first date of a month is proved in a city it is also proved in other city whether they are near or far and whether or not they have a common horizon, provided they have a common night, even though when it is the first part of the night in one of them it is the last part of the night in the other.” [Source]
According to the Common Night criterion, a sighting in location B can be accepted by individuals living in location A as long as both A and B are under the darkness of night at the same time. It is not necessary for the moon to be sightable in location A, and even if it were possible to see the moon in location A, it would not need to appear similar to that in location B with regard to altitude and illumination.
2026 Moonsighting
SIGHTING OF THE MOON
Calculations of the movements of the Sun, Earth, and Moon in relation to each other, and refinements of those calculations through scientific observation, have led to algorithms that can predict the likelihood of seeing the crescent moon for any given date and location. The ability to see the moon is dependent on a variety of factors, such as the amount of time that has elapsed since the new moon, the amount of sunlight in the sky, and the elevation of the moon above the horizon.
The figures (source) show areas of the Earth where the crescent moon marking the beginning of Ramadan 2026 may be sighted (click to enlarge).
According to the first figure, the moon is predicted to be visible by naked eye on the evening of February 18, 2026 in all of the United States.
Predictions for sighting of the crescent moon marking the beginning of Shawwal 2026 (that is, Eid-al-Fitr), are displayed in the second figure (click to enlarge), which indicates that the moon is likely to be visible across the United States on the evening of March 19, 2026.
APPLYING THE COMMON NIGHT CRITERION
The Common Night criterion says that two locations that are both covered by the darkness of night at the same time can accept each other's sightings of the moon, regardless of whether or not the moon can be sighted in one of those locations (see below image of the DC area common night region). As such, the beginning of Ramadan by Common Night criterion is expected to be February 19 as the moon predicted to be easily sightable in the United States the previous evening. For Eid al-Fitr, the moon is likely to be sighted in the United States on March 19; therefore Eid is expected to be on March 20.
APPLYING THE COMMON HORIZON CRITERION
The Common Horizon criterion requires the moon to be sightable with a similar appearance in two locations if one location is to accept the sighting of the other. This requires that the locations have geographic proximity. The moon is expected to be visible in the United States on the evening of February 18. As such, the first day of Ramadan will likely fall on February 19 in the United States. As for Eid-al Fitr, the moon is expected to be sightable in all of the United States on March 19, therefore, Eid-al-Fitr by Common Horizon criterion is expected on March 20.
APPLYING A CALCULATION METHOD
Calculation systems are based on various astronomical parameters, such as altitude above the horizon, minimum angle of separation with the Sun, or simply that the Moon is born.
The most commonly used calculation system in North America is that used by the Fiqh Council of North America, which has determined that the first day of Ramadan is February 18, 2026, and the first day of Shawwal (Eid al-Fitr) is March 20, 2026.
| Summary of Dates for Ramadan and Eid al Fitr 2026 | |||
| Common Night | Common Horizon | Calculation Method* | |
| First Visibility of Ramadan Crescent | February 18 | February 18 | – |
| First Day of Ramadan | February 19 | February 19 | February 18 |
| First Visibility of Shawwal Crescent | March 19 | March 19 | – |
| Eid al Fitr | March 20 | March 20 | March 20 |
* Calculation refers specifically to the Fiqh Council of North America (FCNA).