Daily Talk

Know That You Have Erred

The chapter opens by admitting that the Sages of Israel never agreed on how long a year is, and the wise men of Greece and Persia did not agree either. Then the Rambam spends seven halachot teaching you to calculate the seasons to the unit. Why build a calendar on a number you have just told us is disputed?

Kiddush HaChodesh 9Saturday, August 8, 2026

Know That You Have Erred

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About This Talk

Chapter 9 of Kiddush HaChodesh turns from the moon to the sun: the length of the solar year, the ninety one days and seven and a half hours between one season and the next, the four constellations the sun enters, and the exact procedures for finding the hour, the weekday, and the calendar date of any equinox or solstice forever. Buried in the arithmetic is a startling constraint, that each season may fall only at four fixed hours of the day. The chapter ends by telling the student that if his answer runs past a certain size he should know he has erred and go back and count again.

Know That You Have Erred | The Rambam Experience | The Rambam Experience