At Mount Sinai

1 On the first day of the third month after the Israelites left Egypt—on that very day—they came to the Desert of Sinai.

Read Exodus 19:1 Using Other Translations

In the third month, when the children of Israel were gone forth out of the land of Egypt, the same day came they into the wilderness of Sinai.
On the third new moon after the people of Israel had gone out of the land of Egypt, on that day they came into the wilderness of Sinai.
Exactly two months after the Israelites left Egypt, they arrived in the wilderness of Sinai.