After the Israelites left Egypt, they spent about 40 years traveling in the desert areas of the Sinai Peninsula and the Negev. After this time, they moved on to take control of the land God had promised them. The books of Exodus, Leviticus, and Numbers describe the most important events in this period.
The Bible says that during these hard years in the desert, the tribes unified into a nation. In Sinai, they became one people with one God and one national goal, to conquer Canaan.
Numbers 33:38 and Deuteronomy 1:3 say Israel wandered in the wilderness for 40 years. The number 40 is sometimes used to mean “a long time” or a large round number, and not exactly 40. But in these stories, many exact dates are given. This implies it was a literal 40 years. However, it is hard to know when this period began and ended.
According to 1 Kings 6:1, Solomon began building the temple 480 years after the Israelites left Egypt. The building of the temple began about 960 BC. This means the Israelites left Egypt around 1440 BC (an event known as the exodus). Israel's conquest of Canaan was about 1400 BC. However, scholars date the exodus and conquest to 1290–1250 BC due to certain discoveries of material remains from ancient history. There is no convincing proof for either timeline.
Within the 40 years of wanderings, there are detailed accounts of the first year and a half spent in the desert, from the exodus to the return of the spies (Exodus 12–Numbers 14). Also, more details are provided about the final year of the conquest of Transjordan (Numbers 20–Deuteronomy 34). Not much is known about the years in between when the tribes camped near oases like Kadesh-barnea. The stories described in Numbers 15–17 likely happened during this time that we do not know much about.