the two years. The lunar year consists of three hundred and fifty-four days and a fraction of a day—a fifth or a sixth. It is spoken of as three hundred and sixty days only by rounding up, in keeping with customary practice—the Arab practice of rounding up incomplete units when reckoning days, months, and years.

The solar year, however, consists of three hundred and sixty-five days and a fraction of a day: one quarter. Thus, the difference between them is just under eleven days, amounting to a year every thirty-three and one-third years. Hence Allah, Exalted is He, says:

“And they remained in their cave for three hundred years and exceeded that by nine.”

It has been said that this means three hundred solar years, with “and exceeded that by nine” referring to reckoning by lunar years. Observing both these cycles is customary among many peoples who follow the two Scriptures, owing to the alterations they have made. I believe this was also the practice of the Magi.

As for those who define the year by a natural cycle and the month numerically, this is the reckoning of the Romans, Syrians, Copts, and others like them among the Sabians and polytheists. They reckon the month of Kānūn and similar months by a fixed number of days, while determining the solar year by the sun’s course.

The fourth category is to define the month by a natural cycle and the year numerically. This is the practice of the Muslims and those who follow the same approach. Now, those who define the year by a natural cycle do not rely