As we saw in the previous chapter, the calendar expert Professor Bickerman stated, ‘The pre-Babylonian time reckoning of the ancient Hebrews is virtually unknown’, and the Jewish scholar Sacha Stern wrote, ‘We return to the pre-exilic period … calendar reckoning in the early biblical period remains completely obscure.’ In this chapter we will find this ‘lost calendar’ of early Israel.

According to the book of Exodus, God instructed Moses and Aaron to change the first month of the calendar they were using so that the Exodus from Egypt marked the start of their new year. This was the only change in the calendar they were asked to make. Interestingly, Exodus pointedly states, ‘The Lord said to Moses and Aaron in Egypt, “This month is to be for you the first month”’ (Exodus 12:1–2). The readers of Exodus would have been well aware that Moses and Aaron were in Egypt; Moses and Aaron had been there throughout the ten plagues of the previous seven chapters of Exodus, so why specifically mention that they were in Egypt here, immediately before making a calendrical statement? I suggest the reason is explicitly to draw readers' attention to the fact that Moses and Aaron were in Egypt and therefore using an Egyptian calendar, the first month of which Moses was now to change.