A characteristic feature of the Babylonian mathematical astronomy is the use of periodically varying functions in the form of sequences of numbers (e.g. arithmetic progressions, zig-zag functions, or piecewise constant step functions) to describe periodically occurring astronomical phenomena. One major achievement of the Babylonian astronomers consists in a very precise determination of the periods of the number sequences used in their ephemeris texts. Any reconstruction of the Babylonian calculation schemes must explain how the fundamental periods or period relations can be determined empirically by such astronomical observations as were compiled in the Babylonian Diaries.

This paper is concerned with the Babylonian moon ephemerides. The fundamental periods used here are the length P⊙ of the more empirically founded and less theoretically than believed until now.