The Israelites arrived in the wilderness of Sinai exactly two months after they left Egypt.
References for Exodus 19:1
After breaking camp at Rephidim, they came to the base of Mount Sinai and set up camp there.
Then Moses climbed the mountain to appear before God. The LORD called out to him from the mountain and said, "Give these instructions to the descendants of Jacob, the people of Israel:
'You have seen what I did to the Egyptians. You know how I brought you to myself and carried you on eagle's wings.
Now if you will obey me and keep my covenant, you will be my own special treasure from among all the nations of the earth; for all the earth belongs to me.
And you will be to me a kingdom of priests, my holy nation.' Give this message to the Israelites."