How do the sun and moon help Muslims measure time?

The short answer

The Quran says the sun and moon are signs and that the moon's phases help people count years and time. Islamic months follow lunar cycles; scholars differ over the role of calculation in establishing their starts [1][2].

Evidence 1 2 3

Explanation

The Quran says Allah made the sun a shining light and the moon a light with phases so people can know the number of years and timekeeping 1. It also states that there are twelve months, including four sacred months 2. The lunar calendar therefore has a religious role in setting dates such as Ramadan and Hajj.

The Prophet ﷺ described the lunar month as sometimes twenty-nine days and sometimes thirty 3. Historically, the start of months has been established through crescent observation. Today, astronomical calculations can predict conjunctions and visibility, but Muslim scholars differ about whether calculation can establish the month for religious practice or should serve only as a guide.

Follow the method adopted by a trustworthy local religious authority or community for fasting and Eid, and be considerate when Muslims follow recognized methods that differ. Astronomy is useful for understanding the sky and planning time; it does not itself settle every jurisprudential question. Ask a qualified scholar about the practice in your region.

The evidence

  1. 1
    Quran Yunus · 10:5

    The sun and moon's phases help people count years and time.

    هُوَ ٱلَّذِي جَعَلَ ٱلشَّمۡسَ ضِيَآءࣰ وَٱلۡقَمَرَ نُورࣰ ا وَقَدَّرَهُۥ مَنَازِلَ لِتَعۡلَمُواْ عَدَدَ ٱلسِّنِينَ وَٱلۡحِسَابَۚ مَا خَلَقَ ٱللَّهُ ذَٰلِكَ إِلَّا بِٱلۡحَقِّۚ يُفَصِّلُ ٱلۡأٓيَٰتِ لِقَوۡمࣲ يَعۡلَمُونَ ۝٥

    It is He who made the sun a shining light and the moon a derived light and determined for it phases - that you may know the number of years and account [of time]. Allah has not created this except in truth. He details the signs for a people who know

  2. 2
    Quran At-Tawba · 9:36

    The Quran states that the year has twelve months, four of them sacred.

    إِنَّ عِدَّةَ ٱلشُّهُورِ عِندَ ٱللَّهِ ٱثۡنَا عَشَرَ شَهۡرࣰ ا فِي كِتَٰبِ ٱللَّهِ يَوۡمَ خَلَقَ ٱلسَّمَٰوَٰتِ وَٱلۡأَرۡضَ مِنۡهَآ أَرۡبَعَةٌ حُرُمࣱۚ ذَٰلِكَ ٱلدِّينُ ٱلۡقَيِّمُۚ فَلَا تَظۡلِمُواْ فِيهِنَّ أَنفُسَكُمۡۚ وَقَٰتِلُواْ ٱلۡمُشۡرِكِينَ كَآفَّةࣰ كَمَا يُقَٰتِلُونَكُمۡ كَآفَّةࣰۚ وَٱعۡلَمُوٓاْ أَنَّ ٱللَّهَ مَعَ ٱلۡمُتَّقِينَ ۝٣٦

    Indeed, the number of months with Allah is twelve [lunar] months in the register of Allah [from] the day He created the heavens and the earth; of these, four are sacred. That is the correct religion, so do not wrong yourselves during them. And fight against the disbelievers collectively as they fight against you collectively. And know that Allah is with the righteous [who fear Him]

  3. 3
    Hadith Sahih al-Bukhari 1913
    Sahih Bukhari

    The Prophet ﷺ said the lunar month can be twenty-nine or thirty days.

    Narrated Ibn `Umar:The Prophet (ﷺ) said, "We are an illiterate nation; we neither write, nor know accounts. The month is like this and this, i.e. sometimes of 29 days and sometimes of thirty days

    العربية

    حَدَّثَنَا آدَمُ، حَدَّثَنَا شُعْبَةُ، حَدَّثَنَا الأَسْوَدُ بْنُ قَيْسٍ، حَدَّثَنَا سَعِيدُ بْنُ عَمْرٍو، أَنَّهُ سَمِعَ ابْنَ عُمَرَ ـ رضى الله عنهما ـ عَنِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُ قَالَ ‏ "‏ إِنَّا أُمَّةٌ أُمِّيَّةٌ، لاَ نَكْتُبُ وَلاَ نَحْسُبُ الشَّهْرُ هَكَذَا وَهَكَذَا ‏"‏‏.‏ يَعْنِي مَرَّةً تِسْعَةً وَعِشْرِينَ، وَمَرَّةً ثَلاَثِينَ‏.‏

This answer was compiled with the help of AI, using only the verified texts shown here. Every reference links to its source. If you find a mistake, please report it. Updated 2026-09-25

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