Breadcrumb: How long?

In Ex. 40:17, we read that Moses set up the tabernacle in the first day of the first month of the second year. In other words, the Israelite had been out of Egypt exactly one year by the end of Exodus. As a reminder, Ex. 19:1 informs us that the Israelites entered the desert of Sinai on the third month after the Exodus. By quick calculation, this means that they had camped beneath Mount Sinai approximately nine months. Note that it is only in Num. 10 that the Israelites leave Sinai -- in the twentieth day of the second month of the second year (a month and a half later).