A brief comparison between the lunar calendar and the solar one will show you the difference; the lunar calendar is much clearer and easier as the apparent changes in the shape of the moon are noticeable to all people.

Moreover, no human influence may affect the accuracy of this calendar. On the other hand, the solar calendar is complicated and has been subject to great changes over history at the hands of astronomers due to the constant errors in its calculations.

Therefore, in the Qur’an we read what means, “Indeed, the [ordained] number of the months with God is twelve [lunar] months, [as was decreed] in the [Preserved Heavenly] Book of God on the day He created the heavens and the earth. Four of them are sacred- [and] that is the upright religion.” [9:36]

I advise you to search for the history of the Gregorian calendar to see the great changes and amendments that took place in this calendar and nevertheless still not as accurate as the lunar one.

May Allah guide you to the truth.

Allah Almighty knows best.