Why does the date of Eid Al-Adha change every year?

Arab Weather - The dates of religious events are linked to the lunar calendar, that is, the calendar that is based on the phases of the moon, so the dates of Ramadan, Eid al-Fitr, and Eid al-Adha depend on the beginning of the months associated with the birth of the crescent.

The discrepancy in the number of days between the lunar year and the solar year

The lunar year is defined as the period that the moon needs to rotate 12 revolutions around the earth, each cycle represents one month, and the sum of the days of the lunar year consisting of (12) months is about (354) days, and the solar year is the number of days that the earth needs to revolve around the sun cycle It is (365) days, meaning that the number of days of the lunar year is (11) days less than the number of days of the year in the Gregorian calendar followed in the world, and because of the discrepancy between the number of days of the lunar year and the solar year, the lunar calendar moves backwards from 10 to 12 days each General compared to the Gregorian calendar.

And God Almighty has indicated in the Holy Qur’an, indirectly, to the difference between the lunar and solar Sunnah in the story of the Companions of the Cave, in the Almighty saying: (And they remained in their cave three hundred years ...) according to the solar calculation where the earth revolved around the sun (300) times As the Almighty said: (... and increase nine) that is, (309) years according to the lunar calculation, so every 100 solar years corresponds to (103) lunar years.

The date of Eid al-Adha

The blessed Eid al-Adha comes at