Once this is clear, recording and calculating the days of the month falls into this same category, as we explained earlier. If someone records the movements of the sun and moon using abjad letters or similar notation, and calculates how far they have travelled, when they come into conjunction on the night when the moon is hidden, when they stand opposite one another on the night of the full moon, and so forth, such writing and calculation serve only to establish the times people need for dating events, scheduling activities, and similar purposes.

Other nations have done this, establishing their times through writing and calculation, using tables or letters assigned numerical values. They likewise calculate the movements of the sun and moon, making adjustments and corrections using their mean motion, until they ascertain the time of the moon’s disappearance, the full moon, and other such occurrences.

The Prophet, may Allah bless him and grant him peace, explained that we, the unlettered community, do not engage in this kind of writing or perform this kind of calculation. Thus, what his words deny is the use of writing and calculation concerning the days of the month to determine when the crescent disappears and appears. We have already explained that although an unrestricted negation is general in scope, when something in the context clarifies the intended meaning, it shows whether that meaning is specific or general.

When he coupled this with his statements, “The month is thirty days” and “The month is twenty-nine days,” he made it clear that what he meant was that, regarding the crescent, we need neither writing nor