1st Month of the Exodus. They left Egypt. Exodus 12:1-2. They are told to start counting the months beginning with this month as the 1st month of the year.
Exodus 12:1-2
“YHVH said to Moses and Aaron in the land of Egypt, saying, ‘Thus month shall be for you the beginning of the months, it shall be for you the first of the months of the year’.”
2nd month:
Exodus 16:1, 15
They arrive in the Wilderness of Sin, which is between Elim and Sinai. They receive manna from heaven. (Sin -“to be muddy”; Elim – “mighty ones”; Sinai – “thorns”);
3rd month/4th Month
They arrive in the Wilderness of Sinai. Here YHVH prepared them to receive His Living Word, His teaching and instruction. Exodus 19:1 – 31:18. Moses was on the mountain for 40 days/40 nights.