Qur

And He has appointed the night for rest/stillness [for human beings-10:67;27:86;28:73;40:61].

And appointed the Sun and Moon for reckoning [computation, calculation, measuring, visualization].

These are the equations/settings of relations/relativity by the One Who has absolute Dominance/ Control/Command and Absolute Knowledge. [6:96]

He is the One Who has given the Sun characteristic of radiating heat and visible light; and to the Moon of reflecting visible light.

And He appointed the stages/spaces of the Moon so that you people may know the count/number of [Lunar] years and calculations and equations. [Read with 36:39;84:18] [10:05]

And the Moon; We have measured/proportioned it to stages/spaces traversed in journeying until it returns to the position/space resembling in appearance like the old dry palm branch. [36:39]

And they, the youths stayed in their cave for three hundred years and those [masculine-Moons] added nine years. [In 300 solar years Moons add nine making equivalent to 309 lunar years] [18:25]

You the Messenger [Sal'lallaa'hoalaih'wa'salam] advise, "Allah knows exactly/accurately the time duration they stayed [in that condition]. The invisible/hidden secrets of the Skies and the Earth are for Him the Exalted.

You keep watching/observing about it and keep listening [what people gossip about this episode without indulging in controversy and enquiry, as advised in 18:22]

* Breast feeding period is also mentioned two years in 31:14 and combined period of conception and breast feeding is mentioned as thirty months in 46:15 which shows that a newly married woman could deliver a child after 6 months of marriage.

We can clarify the time referred to in the verse thus: 300 years x 11 days (the difference which forms every year) = 3,300 days. Bearing in mind that one solar year lasts 365 days, 5 hours, 48 minutes and 45.5 seconds, 3,300 days/365.24 days = 9 years. To put it another way, 300 years according to the Gregorian calendar is equal to 300+9 years according to the Hijri calendar. As we can see, the verse refers to this finely calculated difference of 9 years. (Allah knows best.) There is no doubt that the Qur'an, which contains such pieces of information, which transcended the everyday knowledge of the time, is a miraculous revelation.

A calendar is a system of organizing days for social, religious, commercial or administrative purposes. This is done by giving names to periods of time, typically days, weeks, months, and years. A date is the designation of a single, specific day within such a system. Periods in a calendar (such as years and months) are usually, though not necessarily, synchronized with the cycle of the sun or the moon. Many civilizations and societies have devised a calendar, usually derived from other calendars on which they model their systems, suited to their particular needs.

The English word calendar is derived from the Latin word kalendae, which was the Latin name of the first day of every month

A lunisolar calendar is a calendar in many cultures whose date indicates both the moon phase and the time of the solar year. If the solar year is defined as a tropical year, then a lunisolar calendar will give an indication of the season; if it is taken as a sidereal year, then the calendar will predict the constellation near which the full moon may occur. Usually there is an additional requirement that the year have a whole number of months, in which case most years have 12 months but every second or third year has 13.

The Hebrew, Buddhist, Hindu, Burmese, Bengali, and Tibetan calendars, as well as the traditional Chinese, Japanese, Vietnamese, Mongolian and Korean calendars, plus the ancient Hellenic, Coligny, and Babylonian calendars are all lunisolar. Also some of the ancient pre-Islamic calendars in South Arabia followed a lunisolar system.^[1] The Chinese, Coligny and Hebrew^[2] lunisolar calendars track more or less the tropical year whereas the Buddhist and Hindu lunisolar calendars track the sidereal year. Therefore, the first three give an idea of the seasons whereas the last two give an idea of the position among the constellations of the full moon. The Tibetan calendar was influenced by both the Chinese and Hindu calendars. The Germanic peoples also used a lunisolar calendar before their conversion to Christianity.

The Islamic calendar is lunar, but not a lunisolar calendar because its date is not related to the sun. The civil versions of the Julian and Gregorian calendars are solar, because their dates do not indicate the moon phase — however, both the Gregorian and Julian calendars include undated lunar calendars that allow them to calculate the Christian celebration of Easter, so both are lunisolar calendars in that respect.

A year (Old English gēar, Gothic jēr, Runic Jēran) is the orbital period of the Earth moving around the Sun. For an observer on the Earth, this corresponds to the period it takes the Sun to complete one course throughout the zodiac along the ecliptic.

In astronomy, the Julian year is a unit of time, defined as 365.25 days of 86400 SI seconds each (no leap seconds).^[1]

There is no universally accepted symbol for the year as a unit of time. The International System of Units does not propose one. A common abbreviation in international use is a (for Latin annus), in English also y or yr.

Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by changes in weather, hours of daylight, and consequently vegetation and fertility. In temperate and subpolar regions, generally four seasons are recognized: spring, summer, autumn and winter, astronomically marked by the Sun reaching the points of equinox and solstice, although the climatic seasons lag behind their astronomical markers. In some tropical and subtropical regions it is more common to speak of the rainy (or wet, or monsoon) season versus the dry season.

A calendar year is an approximation of the Earth's orbital period in a given calendar. A calendar year in the Gregorian calendar (as well as in the Julian calendar) has either 365 (common years) or 366 (leap years) days.

The word "year" is also used of periods loosely associated but not strictly identical with either the astronomical or the calendar year, such as the seasonal year, the fiscal year or the academic year, etc. By extension, the term year can mean the orbital period of any planet: for example, a "Martian year" is the time in which Mars completes its own orbit. The term is also applied more broadly to any long period or cycle, such as the "Great Year".^[2]