Moon Sighting Methods Used by Muslims

Muslims determine the beginning of Ramadan by following a lunar calendar that is based on the movement of the moon. Unlike the common solar calendar, which is based on the sun and remains fixed within the seasons, the Islamic calendar follows the moon’s cycle.

The Lunar (Synodic) Month

A lunar month lasts about 29 and a half days, which is why Islamic months are either 29 or 30 days long and never exceed thirty days. Over the course of a year, this makes the Islamic calendar about 10 to 11 days shorter than the solar calendar. As a result, Ramadan gradually moves through all seasons over time spanning a 33 year cycle.

Because each month begins with the appearance of the new crescent moon, the start of Ramadan depends on when that moon is confirmed. This method goes back to the teachings of the Prophet, peace be upon him, and has been practiced by Muslims for centuries. However, since visibility of the moon can vary from place to place and from night to night, Muslims may begin Ramadan on different days.

How Moon Sightings Are Followed

Over time, different approaches have developed for how moon sightings are followed. Each of these approaches has roots in the Quran, the Prophetic Tradition, and the classical scholarship, and is supported by different scholarly interpretations.

• Some communities rely on local sighting, meaning that people in the same city or region attempt to see the moon and base their decision on that observation. This approach emphasizes direct, nearby visibility and close community involvement.

• Others follow a regional approach, in which an entire country or a group of nearby countries accepts a shared sighting. This method helps unify larger populations and reduce differences within a region.

• Still others follow a global approach, accepting a confirmed sighting from anywhere in the world. This view emphasizes the idea that the moon is one for all Muslims and that a valid sighting in one place can apply everywhere.

Tools Used to See the Moon

Muslims also differ in the tools they use to observe the moon.

• Many rely only on the naked eye, following the most traditional practice and emphasizing simplicity and direct observation.

• Others allow the use of telescopes and optical aids, which help locate the crescent more clearly, especially in difficult viewing conditions.

• In modern times, some scholars and institutions also use astronomical calculations that can predict when and where the moon is likely to be visible. These calculations are often used to organize, verify, or support sightings rather than replace them completely.

The use of different tools reflects advancement in technology while trying to remain faithful to Islamic principles.

Why Differences Happen

Because of these varying approaches and tools, Muslims do not always begin Ramadan on the same day. Some choose to follow only what is seen locally. Others trust broader regional or global reports. Some believe that the body of Islamic scholarship allows for careful use of scientific data to determine when sighting is possible, whether within local, regional, or global systems.

These differences are not based on neglecting religious teachings. Rather, they come from sincere efforts to understand and apply the Quran and the Prophet Tradition in different circumstances.

All of these groups are trying to follow what they believe is the most correct and faithful method. Recognizing this helps promote patience, mutual respect, and unity within the Muslim community, especially during the blessed month of Ramadan.

Practice in the West

In many Western countries, especially in North America, many mosques follow Saudi Arabia’s announcement because it is to the East of them and sees the moon earlier. Saudi Arabia has been moving more toward calculation-based methods, and some major bodies of Islamic jurisprudence have begun advocating for the same.

At the same time, many scholars and communities still prefer traditional local and visual moon sightings and do not agree with use of calculations in order to declare the start of Ramadan.

Comparison With the Jewish Calendar

Both Muslims and Jews originally follow lunar calendars. However, over time, Jews developed a fixed lunar-solar system. Several centuries ago, Jewish scholars introduced a “leap month” that is added every few years. This keeps Jewish holidays in roughly the same season each year and aligned with the solar calendar.

Muslims, however, do not use a leap month. The Islamic calendar remains purely lunar. As a result, Ramadan and other Islamic months move through all seasons over time over 33 years. This is a deliberate obligatory choice rooted in scripture and will not be changed.

Despite these differences, the shared goal is sincere worship and faithfulness to religious tradition.

Some Key Scriptural References

The Quran establishes that fasting in Ramadan becomes obligatory when the month is known to have begun, and the Prophet, peace be upon him, clarified that this is primarily determined through sighting the new moon, with the instruction to complete thirty days when visibility is blocked. Classical scholars therefore relied mainly on direct observation, understanding key terms in the Quran and the Prophetic Tradition as referring to physical sighting.

At the same time, differences in how certain phrases are interpreted, such as “witnessing” the month, “estimating” it, and the statement that the community does not calculate, have led some later scholars to consider reliable astronomical calculations as a valid means of establishing the month. These varying interpretations, rooted in the same foundational texts, explain why Muslims today may follow different methods while each seeks to remain faithful to Islamic law and its principle of ease.

Verse in the Quran stating when the month of Ramadan should begin

• ﴿شَهْرُ رَمَضَانَ الَّذِي أُنْزِلَ فِيهِ الْقُرْآنُ هُدًى لِلنَّاسِ وَبَيِّنَاتٍ مِنَ الْهُدَىٰ وَالْفُرْقَانِ ۚ فَمَنْ شَهِدَ مِنْكُمُ الشَّهْرَ فَلْيَصُمْهُ ۖ وَمَنْ كَانَ مَرِيضًا أَوْ عَلَىٰ سَفَرٍ فَعِدَّةٌ مِنْ أَيَّامٍ أُخَرَ ۗ يُرِيدُ اللَّهُ بِكُمُ الْيُسْرَ وَلَا يُرِيدُ بِكُمُ الْعُسْرَ وَلِتُكْمِلُوا الْعِدَّةَ وَلِتُكَبِّرُوا اللَّهَ عَلَىٰ مَا هَدَاكُمْ وَلَعَلَّكُمْ تَشْكُرُونَ ۝﴾ (سُورَةُ البَقَرَة ٢:١٨٥)

2:185 The month of Ramadan^[1] ˹is that˺ in which was revealed the Qur'an, a guidance for the people and clear proofs of guidance and criterion. So whoever witnesses^[2] ˹the new moon of˺ the month, let him fast it; and whoever is ill or on a journey - then an equal number of other days. Allah intends for you ease and does not intend for you hardship and ˹wants˺ for you to complete the period and to glorify Allah for that ˹to˺ which He has guided you; and perhaps you will be grateful.

Prophetic Tradition: The beginning and ending of the Ramadan is based on the moon

• «صُومُوا لِرُؤْيَتِهِ وَأَفْطِرُوا لِرُؤْيَتِهِ فَإِنْ غُبِّيَ عَلَيْكُمْ فَأَكْمِلُوا عِدَّةَ شَعْبَانَ ثَلاَثِينَ» (البخاري ١٩٠٩ متفق عليه)

"˹Start˺ fasting ˹the month˺ upon seeing it (the moon), and break ˹fasting the month˺ upon seeing it. If it is hidden for you (as a result of an overcast at the start of the month), then complete thirty days of Shaban (the prior month)." (Authentic)

Prophetic Tradition: Begin and end Ramadan fasting upon sighting the crescent moon or estimate it

• «لاَ تَصُومُوا حَتَّى تَرَوُا الْهِلاَلَ، وَلاَ تُفْطِرُوا حَتَّى تَرَوْهُ، فَإِنْ غُمَّ عَلَيْكُمْ فَاقْدُرُوا لَهُ» (البخاري ١٩٠٦ متفق عليه)

"Do not fast unless you see the crescent ˹of Ramadan˺, and do not give up fasting till you see the crescent ˹of Shawwal, the next month˺ , but if the sky is overcast ˹and you cannot see the moon˺, then estimate^[3] for it. (Authentic)

Prophetic Tradition: Islamic law is easy and does not require complex calculations or science

• «إِنَّا أُمَّةٌ أُمِّيَّةٌ لاَ نَكْتُبُ وَلاَ نَحْسُبُ. الشَّهْرُ هَكَذَا وَهَكَذَا - يَعْنِي مَرَّةً تِسْعَةً وَعِشْرِينَ وَمَرَّةً ثَلاَثِينَ» (البخاري ١٩١٣ متفق عليه)

"We are an unlettered nation; we neither write, nor do we calculate^[4]. The month is like this and this, ˹the narrator added˺ meaning sometimes of twenty nine days and sometimes of thirty." (Authentic)