Exodus 19 informs us of Israel’s arrival at the desert around Mt. Sinai; Numbers 10 tells how the people packed up and started on their march to the Promised Land. Exodus 19:1 probably refers to the first day of the third month of the first year as the date the Israelites arrived at Mt. Sinai. Numbers 10:11 gives the 20th day of the second month of the second year as the date when the desert trek began. Even with these data, we cannot calculate the precise number of days spent at Sinai because we don’t know whether the months referred to in the Torah were lunar months, with 28–29 days, or luni-solar months, with 30–31 days. If we assume a solar calendar with 30 or 31 days per month, the total stay would have been 355 or 354 days (10 or 11 days fewer than a solar year), or precisely a lunar year.