The first day of the second month, in the second year is precisely one month after the tabernacle had been erected at Mount Sinai (see Exodus 40:17). The Israelites had arrived at Mount Sinai in the third month of the first year (Exodus 19:1), which means that they have now remained at the site for an entire period of eleven months. Now that God had taken residence in and amongst his sinful people, and having instituted the means by which his holy wrath would be satisfied (the theme of Leviticus), it means that the Israelites were now in a position to move forward in his strength and under his protection. They were now in a position to take the Promised Land.
1 The LORD spoke to Moses in the wilderness of Sinai, in the tent of meeting, on the first day of the second month, in the second year after they had come out of the land of Egypt, saying,