Qur'an - Calculation of Time & Calendar

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More than 1400 years ago, when people thought that the Sun was the size of an apple and the Earth was flat, Quran described the relationship of the Sun & moon and how precisely calculated that relationship is. It describes how night & day are measured and can't overrun each other. All were important clues to humans that the movement & relationship of sun and moon can be used to calculate the time and calendar. One of the most well known chapters of Quran begins with "swearing" to "Time" highlighting the importance of Time and making humans to ponder about it (investigate it) . 

وَالْعَصْرِ إِنَّ الْإِنسَانَ لَفِي خُسْرٍ إِلَّا الَّذِينَ آمَنُوا وَعَمِلُوا الصَّالِحَاتِ وَتَوَاصَوْا بِالْحَقِّ وَتَوَاصَوْا بِالصَّبْرِ

"By the ˹passage of˺ time!  Indeed, mankind is in loss, Except for those who have believed and done righteous deeds and advised each other to truth and advised each other to patience." 103:1-3

Verse 36:39 beautifully depicts the graceful journey of the moon, as it gracefully glides through its calculated phases in the 12-month lunar calendar, ultimately returning to its familiar crescent shape. This imagery is reminiscent of an ancient date tree branch gently bending under the weight it carries.

Verse 36:40 poetically captures the awe-inspiring movement of everything in the vast universe, as if they were gracefully swimming along in their designated orbits.

Moreover, God has ingeniously established a perfect equilibrium between the Sun and the moon, meticulously aligning their orbits, speeds, rotations, and gravitational forces. This intricate balance ensures that they will never surpass one another, harmoniously coexisting in the cosmic dance.

Additionally, the Quran enlightens us by revealing that the length of both night and day is precisely calculated and predetermined. This revelation serves as a gentle nudge, encouraging us to explore and uncover the fascinating mechanisms behind this divine orchestration.

لنَّهَارِ وَكُلٌّ فِي فَلَكٍ يَسْبَحُونَ

"And the moon, for which We have determined (calculated & measured) phases [which it must traverse] till it becomes like an old date-stalk, dried-up and curved; It is not permitted to the Sun to catch up the Moon, nor can the Night outstrip the Day: All celestial bodies in the universe swim along in (their own) orbit (according to Law & calculation)." 36:39-40

أَلَمْ تَرَ أَنَّ اللَّهَ يُولِجُ اللَّيْلَ فِي النَّهَارِ وَيُولِجُ النَّهَارَ فِي اللَّيْلِ وَسَخَّرَ الشَّمْسَ وَالْقَمَرَ كُلٌّ يَجْرِي إِلَى أَجَلٍ مُّسَمًّى وَأَنَّ اللَّهَ بِمَا تَعْمَلُونَ خَبِيرٌ

"Do you not see that Allah causes the night to enter the day and causes the day to enter the night and has subjected the sun and the moon, each running [its course] for a specified term, and that Allah , with whatever you do, is Acquainted?" 31:29

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يُولِجُ اللَّيْلَ فِي النَّهَارِ وَيُولِجُ النَّهَارَ فِي اللَّيْلِ وَسَخَّرَ الشَّمْسَ وَالْقَمَرَ كُلٌّ يَجْرِي لِأَجَلٍ مُّسَمًّى

ذَلِكُمُ اللَّهُ رَبُّكُمْ لَهُ الْمُلْكُ وَالَّذِينَ تَدْعُونَ مِن دُونِهِ مَا يَمْلِكُونَ مِن قِطْمِيرٍ

"He causes the night to enter the day, and He causes the day to enter the night and has subjected the sun and the moon -

each running [its course] for a specified term. That is Allah , your Lord; to Him belongs sovereignty.

And those whom you invoke other than Him do not possess [as much as] the membrane of a date seed." 35:13

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The verse below clearly is telling us that the movement of sun and moon are based on precise calculations and rules. In other words, challenging us to discover it! The very first things that humans could discover from such movement (day & night) is the calculation of Time and constructing a precise calendar! Isn't today's technology, manufacturing, living, and other affairs dependent on calculation of Time?!

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الشَّمْسُ وَالْقَمَرُ بِحُسْبَانٍ

"The sun and the moon [move] by precise calculation (and rules)," 55:5

Verse 25:45 describes the relationship of Sun and shadows of objects (sundial).

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أَلَمْ تَرَ إِلَى رَبِّكَ كَيْفَ مَدَّ الظِّلَّ وَلَوْ شَاء لَجَعَلَهُ سَاكِنًا ثُمَّ جَعَلْنَا الشَّمْسَ عَلَيْهِ دَلِيلًا

"Have you not seen how your Lord spread the shadow. If He willed, He could have made it still then We have made the sun its guide

[i.e. after the sunrise, it (the shadow) squeezes and vanishes at noon and then again appears in the afternoon

with the decline of the sun, and had there been no sun light, there would have been no shadow]."  25:45

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وَجَعَلْنَا اللَّيْلَ وَالنَّهَارَ آيَتَيْنِ فَمَحَوْنَا آيَةَ اللَّيْلِ وَجَعَلْنَا آيَةَ النَّهَارِ مُبْصِرَةً لِتَبْتَغُواْ فَضْلاً مِّن رَّبِّكُمْ وَلِتَعْلَمُواْ عَدَدَ السِّنِينَ وَالْحِسَابَ

وَكُلَّ شَيْءٍ فَصَّلْنَاهُ تَفْصِيلاً

"We have made the Night and the Day as two (of Our) Signs: the Sign of the Night have We obscured, while the Sign of the Day We have made to enlighten you; that you may seek bounty from your Lord, and that you may know the number and count of the years: all things have We explained in detail." 17:12

Calculation of Time using Pulsars!​

Verses 86:1-3 beautifully depict a celestial phenomenon known as a pulsar, also referred to as the Knocking star or PSR B0329+54 Pulsar. For an in-depth understanding of this fascinating pulsar and its connection to the mentioned verses, we invite you to explore our page titled "Sound of the PSR B0329+54 Pulsar." One intriguing aspect of these verses is that the Quran explicitly encourages us to delve into the research of this celestial body, hinting at its intricate nature by posing a thought-provoking question. It is worth noting that some pulsars rotate at an astonishing speed of 600 times per second, making them invaluable tools for astronomers. In fact, in 1983, certain types of pulsars surpassed atomic clocks in terms of their remarkable timekeeping precision.

الطَّارِقُ النَّجْمُ الثَّاقِبُ​

"By the sky and the Knocking Star; and what will convey to you what the Knocking Star is? It is the Piercing Star" 86:1-3

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Calculation of Time using Sidereal Day!

 Quran gives us a clue in Chapter 53 about using Sidereal Day measurements and far away stars as the reference point instead of the Sun. For details, please see the page about "Sirius".

وَأَنَّهُ هُوَ رَبُّ الشِّعْرَى

"And that it is He alone who is the Lord and Sustainer of Sirius"  53:49 

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فَكَانَ قَابَ قَوْسَيْنِ أَوْ أَدْنَى

"And was at a distance of two bows' length or (even) nearer" 53:9

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Quran and the Calendar

​The commencement of each month in the Islamic calendar coincides with the birth of a new lunar cycle. Traditionally, this is determined by observing the crescent moon, which signifies the end of the previous lunar cycle and the beginning of a new month. As a result, each month can consist of either 29 or 30 days, depending on the visibility of the moon and the astronomical positioning of the earth. In verse 9:36, we are urged to embrace a 12-month calendar, as it is divinely ordained by God. It is fascinating to note that the movement of the Sun, moon, Earth, and the 12 months has been intricately designed by God since the inception of the universe. Their creation was not a mere coincidence.
 

إِنَّ عِدَّةَ الشُّهُورِ عِندَ اللّهِ اثْنَا عَشَرَ شَهْرًا فِي كِتَابِ اللّهِ يَوْمَ خَلَقَ السَّمَاوَات وَالأَرْضَ مِنْهَا أَرْبَعَةٌ حُرُمٌ ذَلِكَ الدِّينُ الْقَيِّمُ

فَلاَ تَظْلِمُواْ فِيهِنَّ أَنفُسَكُمْ وَقَاتِلُواْ الْمُشْرِكِينَ كَآفَّةً كَمَا يُقَاتِلُونَكُمْ كَآفَّةً وَاعْلَمُواْ أَنَّ اللّهَ مَعَ الْمُتَّقِينَ

"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]." 9:36

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It can't be clearer than this! God is telling us that we can utilize the crescent new moons to measure time!

....يَسْأَلُونَكَ عَنِ الأهِلَّةِ قُلْ هِيَ مَوَاقِيتُ لِلنَّاسِ

"They ask you, [O Muhammad], about the new moons. Say, "They are measurements of time for the people..." 2:189

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هُوَ ٱلَّذِى جَعَلَ ٱلشَّمْسَ ضِيَآءً وَٱلْقَمَرَ نُورًا وَقَدَّرَهُۥ مَنَازِلَ لِتَعْلَمُوا۟ عَدَدَ​

 ٱلسِّنِينَ وَٱلْحِسَابَ مَا خَلَقَ ٱللَّهُ ذَٰلِكَ إِلَّا بِٱلْحَقِّ يُفَصِّلُ ٱلْـَٔايَـٰتِ لِقَوْمٍ يَعْلَمُونَ

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 10:5

وَجَعَلْنَا اللَّيْلَ وَالنَّهَارَ آيَتَيْنِ فَمَحَوْنَا آيَةَ اللَّيْلِ وَجَعَلْنَا آيَةَ النَّهَارِ مُبْصِرَةً لِتَبْتَغُواْ فَضْلاً مِّن رَّبِّكُمْ وَلِتَعْلَمُواْ عَدَدَ السِّنِينَ

وَالْحِسَابَ وَكُلَّ شَيْءٍ فَصَّلْنَاهُ تَفْصِيلاً

"We have made the Night and the Day as two (of Our) Signs: the Sign of the Night have We obscured, while the Sign of the Day We have made to enlighten you; that you may seek bounty from your Lord, and that you may know the number and count of the years: all things have We explained in detail" 17:12

Comparison of Solar year and Lunar year

Another interesting fact exists in the following verse that is also related to the "people of the cave".  Please also see "Ears are active during sleep" and "Importance of moving during sleep".  The verse basically says that the people of the cave were sleep for 300 years plus 9 years.  Why not saying "309 years"?  A Lunar year is roughly 354 days while a Solar year is 365 days.  Now, the first portion of the verse is giving the number of lunar years and the 2nd part of the verse gives the equivalent days for Solar year.  Basically, 300 solar years is equivalent of 309 lunar years!  That's absolutely amazing.  Please see the calculation below:

(300 lunar years) x (354 lunar days) = 106200 = This is the number of days in 300 lunar years

(9 lunar years) x (354 lunar days) = 3186  = This is the number of days in 9 lunar years

106200 + 3186 = 109386 = This is the total number of days in 309 lunar years

109386 / (365 solar days)  = 299.68 = This is the number of solar years; In other words 300 solar years

وَلَبِثُوا۟ فِى كَهْفِهِمْ ثَلَـٰثَ مِا۟ئَةٍ سِنِينَ وَٱزْدَادُوا۟ تِسْعًا

So they stayed in their Cave three hundred years, and (some) add nine (more)   18:25